The new building replaced the Murray Hill Hotel (1883), but only after the hotel residents' resistance had led to delays and lengthy court battles.

The 36-storey building is built on an L-shaped plot, with the wing stepping back on the 40th Street side and the main mass rising on Park Avenue. Above the base, the tower rises to a set-back top with illuminated numbers indicating the building's street number. The facade has piers of white brick, with vertical stripes of glass and aluminium spandrels between.

The most notable feature of the building was its bulk, exemplified by the 2,790 m² floors of the 13-storey base, enabled by the introduction of effective illumination and air-conditioning for the deep interiors of the large base. The massing resulted in a total interior space of 76,700 m².

As a large speculative office tower that maximized the built space for its plot, the 100 set the trend for International Style construction in the following decades.

The organization had been searching for a site to locate to, and when developer William Zeckendorf's plans for the so-called "X City" to these East River blocks he had collected fell through, the site was proposed as a home for the U.N.. As the city was unable to purchase the site itself, John D. Rockefeller, Jr. bought the land for the complex for $8.5 million and donated it to the city in December 1945.

An international committee of architects, called the United Nations Board of Design, was assembled in 1947 and consisted of ten architects (including Brazilian Oscar Niemeyer and Swede Sven Markelius) and was assisted by numerous consultants. Work on the plans was started in January 1947.

Of individual architects' proposals, that by Le Corbusier, representing France, was chosen as the basis for further design. His "scheme 23A" from March 1947 included, among the placement and massing of the actually completed buildings (like the Secretariat as a high-rise slab), also an (unrealized) east-west slab on the north end of the site.

Razing of the site was begun in July 1947 and ground for the Secretariat building broken on September 14, 1948. The cornerstone was laid on October 24, 1949 and the Secretariat was completed in spring 1950. The whole complex was ready by 1952.

Despite the strong criticism against its scale (as opposed to General Assembly and Conference buildings) and its interior design, the 39-storey, 154 m tall Secretariat building was nevertheless an impressive modernist landmark, and it influenced commercial building for years after its completion.

The east and west facades' blue-green-toned Thermopane windows were chosen because they lessened the heating effect of the sun, thus reducing the need for a more effective air-conditioning. The curtain wall of the building is truly all-glass, as also the spandrels between the window rows of the floors are of glass, only painted black on the inside surface. Although Le Corbusier opposed this arrangement and wanted to use normally opening windows along with brise soleil awnings as a guard against sunheat -- related to the fixed metal rod screens that have become so commonplace in the 1990s -- the curtain wall was to epitomize the whole skyscraper design from that point on. The windowless north and south ends of the Secretariat are clad in marble plates from Vermont.

The glass walls are interrupted by air-conditioning intake grilles on 6th, 16th, 28th and 39th floors, extending the whole width of the facade (image). The structural columns form 28 feet (8.5 meters) wide bays along the outer wall and the glass walls are cantilevered 0.8 meters from the column line to enable an uninterrupted curtain wall.

On the 38th floor of the building are the UN Secretary General's offices. At the top is a high aluminium grille to conceal the equipment on the roof.

Bronze sculpture Single Form (1962-63) by Barbara Hepworth stands outside the Secretariat.

The United Nations is seeking ways to make extensive repairs and updates to the building that is plagued by asbestos, lead paint and concrete falling off, as well as inefficient ventilation and windows and a lack of fire sprinklers. Renovation could last until 2012, cost $1 billion and possibly require the construction of a new office tower to the south of 42nd Street to house the Secretariat's activities in the meantime.

The magazine's building was begun two years after the Best & Company high-rise department store on the western blockend (later to be replaced by the Olympic Tower) started the post-war construction on Fifth Avenue. The Look Building was a similar catalyst on the Madison side, replacing St. Patrick's Cathedral College (1893).

The 23-storey building's steel frame (built in only 12 weeks of hectic work) enables the facades to have full strip windows with narrow mullions, wrapping continuously around the three facades, forming alternating bands with the white brick spandrels. All the corners of the building are rounded up to the water tower enclosing at the top at 93 meters, doubling its form on the Madison Avenue facade upper floors. Above the first setback, the symmetrical sidestreet facades even curve within themself to form a west wing set back from the street line.

The full-block site had been acquired as early as in the early 1940s, but the construction on the already-excavated site could get underway only after the war.

The 42-storey building has a massing that rises as a set-back full-block portion to half the total height and the unsetback tower rises to 156 meters on the eastern end of the block. The building is orientated along the north-south street grid, with the diagonal direction on the Broadway side followed by the massing of the wings.

The building is clad in green-hued brick and the strip windows have mullions painted in bright red.

For the use of its industrial tenants, the building was also equipped for off-street loading and unloading of trucks.

Announced in 1949, the building was, imaginatively, called the Chrysler Building East. Despite having its main entrance on Third Avenue side, the address was given as a 42nd Street one -- due to the then-seedier nature of the avenue. With the demolition of the disturbing Third Ave. Elevated Railway in 1956 -- which started a general development boom on the avenue -- the address was accordingly changed to 666 Third Avenue.

The 32-storey building rises set-back from a block-wide base with a ground floor of black granite. Originally clad in white brick, the uniform window openings on the slab-form tower changed into continuous vertical striping for the top floors.

The Chryslers occupied the ends of the blocks, but the properties between remained in other hands, so an underground connection was dug to connect the two buildings.

After the Tishman Speyer Properties bought both the buildings, as well as the intervening low-rises, in 1998, Philip Johnson was brought in to renovate the East Building, as it was to be called. Not only was the building clad in a dark blue curtain wall, but the interior arrangement was also changed radically. A 13,500 m² addition to the western side changed the building from one with elevators located to one side to a center core building.

The new Chrysler Center incorporates all the buildings on the southern blockfront facing 42nd Street,with a new Johnson-designed lobby connecting the structures.

In May 2001, the Chrysler Trylons, a Philip Johnson-designed pyramidal extravaganza of blue-grey glass was completed between the two Chrysler Buildings. The three different three-sided pyramids (consisting of 535 panes of glass) cover a, yes, three-level space, planned for retail and restaurant uses.

In 2002, Tishman Speyer sold its 75 percent stake in the building for $224 million for the German Commerz Leasing und Immobilien.

Although originally planned to be built in Chicago, Lever brothers chose to relocate to New York City for advertising reasons. SOM, the designers of the new Lever headquarters, were spurred by the company president Charles Luckman, also an architect, to design along modern and "American" lines. (Luckman returned to architecture after his precidency was over, and in fact worked as a partner with Pereira & Luckman to design the first proposal for the cross-corner Seagram Building in 1954.)

This 24-storey building replaced the heavy (and heavy-looking as well) masonry walls of the contemporary skyscrapers with mere green-tinted glass curtains and stainless steel sheathing. Although the building was also criticized for its appearance amidst the old masonry apartment houses, it was nevertheless usually taken with enthusiasm as a pioneer of the new style.

The building was also revolutionary in being the first skyscraper to utilize the clause in city zoning regulations that allowed a building to rise straight up without setbacks if it occupied only a quarter of the plot. It houses 26,000 m² of total space, of which 13,900 is for offices. Notable was also the fact that the building was planned from the outset to be occupied merely by the owner, Lever Brothers Co., rather than letting part of the building to outside clients. Unilever has since almost vacated the building, occupying today only the four top floors of the building, with the rest available for renting.

The basement houses a 63-car garage, the only portion of the building utilizing the whole plot area -- the area used by the office tower would, in fact, cover the plot with a mass only eight-storey tall.

On the street level there is a garden atrium, separated from the street by metal-sheathed columns carrying the low "perimeter" base of the building. Landscape designer Isamu Noguchi planned a 14-piece sculpture garden to the atrium space, but the plan was eventually not carried out (image) (the garden was finally added in 2002 in a design by landscape architect Ken Smith, following the overall style of Noguchi's design (image)).

The top of the low horizontal base also functions as an outside "elevated" plaza, accessible from the employee cafeteria at the base of the tower.

The vertical main mass of the building raises on columns from the base and is positioned at right angles to Park Avenue, with the wider portion of the tower slab facing south. The tower is set back 30 m from the south building line and 13 m from the north, giving the office premises an unprecedented amount of light and air. It was also the first fully climate-controlled, fixed-windowed office building in NYC. The top three floors, distinguishable on the facade, house technical installations and machinery.

A movable scaffolding was developed especially for the cleaning of the tower's glass walls. The crane unit moves around the perimeter of the flat roof on rails and supports the scaffold. In accordance with the owner, the detergent used in cleaning the windows came from the Lever line of products -- the first product used was Lever's "Handy Andy"...

The extensive interior design of the building was trusted to Raymond Loewy, who was to become one of the most iconic figures in the profession.

In late 1998, the new leasehold owner of the building, RFR Holdings, was negotiating a 99-year ground lease extension for the building. Also the possibility of an addition has been mentioned as there is still 22,300 m² of unused development rights available.

In November 1999, a $10.7 million contract for renovation of the building's facade was awarded to Flour City International, Inc.. The renovation will be designed by Skidmore, Owings & Merrill and supervised by the NYC Historical Society.

Along with the aforementioned sculpture garden addition and previous renovations worth $40 million, RFR is adding a restaurant to the ground floor. The 420 m² restaurant is designed by Marc Newson and will have entrances from both the lobby and 53rd Street.

The facade is, similarly to the Lever Building's, characterized by the horizontal window stripes and vertical top pattern, but the form of the building differs notably from its predecessor. The lower portion of the building occupies the whole building lot and halfway up the building there are series of setbacks before the upper portion rises vertically to the top.

Announced in 1953, the building was the largest office development in NYC since Rockefeller Center: it housed 120,800 m² of space, of which 46,500 was occupied by Socony-Mobil (until 1955 called Socony-Vacuum). At the time of its completion, it was also both the largest centrally air-conditioned commercial building and the largest metal-clad office building in the world.

The 45-storey building has a simple slab form, rising to the height of 174.5 m, set back from the street by lower-floor extensions.

Although originally planned as brick-clad, the facade material was changed to aluminium and eventually to stainless steel in 7,000 panels with a three-dimensional treatment that gives the facade a "rusticated" effect, similarly to the same architects' Alcoa Building in Pittsburgh two years earlier, or the later Tishman Building in NYC. In addition to its aesthetic role and the developers' aspiration for a long-lasting facade treatment, the patterning has also a practical function: it prevents the facade plating from bending.

The building is set on a three-storey base clad in blue glass, with retail spaces and through-building arcades. The lobby is vaulted, reflecting the arched entrances, and has white marble and terrazzo decor.

After Mobil moved its operations to Virginia in 1987, the Hiro Real Estate Company obtained the operating lease, having also given the building a $15 million renovation.

Architects Carson & Lundin were hired to bring the building such Rockefeller Center-like appearance that their Esso (later Time Warner) Building presented. In the course of the design work, the stone cladding was, however, changed to patterned aluminium plating, resulting in the largest aluminium-clad building in NYC so far.

The 30-storey main slab rises from a nine-storey base and there is 115,700 m² of office space inside the building. The building is illuminated at night by floodlights and the illuminated 3.5-meter numbers "666" adorn the top. (In 2002, the numbers were replaced by a blue and red Citigroup logo on three facades.)

The entrance from Fifth Avenue is through two recessed gateways, flanked by retail spaces and sturdy black columns. The entrance lobby is lined in red limestone from Southern France. Isamu Noguchi designed the lobby ceilings and the waterfall adorning the outside gateways by using bent metal profiles -- illuminated for added effect -- as decoration (image). Also the patterned marble floors in the lobby are his handiwork.

The top of the building housed the appropriately named restaurant The Top of the Sixes, affording a view over Midtown, before it was closed in 1996. The restaurant had decor by Raymond Loewy.

Renovated in 1998 under its Japanese owners, Sumitomo Realty and Development (1987, $530 million), Nobutaka Ashihara Associates re-designed the retail spaces and arcade as an expanded, glass-walled entity. The Alitalia airline ticket office by Gio Ponti had been closed a year earlier. Also the top-floor restaurant space was converted into the Grand Havana club.

The original developer firm (in its 1990s form), Tishman Speyer, co-re-obtained the building in 2000 with the German investment group TMW. In 2001 they set to modify the Fifth Avenue street-level frontage by replacing the mid-facade entrance with retail space. The loss of the entrance will be offset by enlarging the 52nd Street entrance and expanding the lobby. Also the interior of the lobby will be restored to its original form.

In 2002, the building was put on sale, hoping to fetch up to $900 million.

The 38-storey, 137-meter building was built on an L-shaped plot, with the building wrapped around the north-eastern corner plot of the blockend. The tower on the southern wing is set back progressively from 40th Street and Sixth Avenue as it rises.

The elevator banks on the building are offset to the west wall, freeing other floor space for offices, with 61,780 m² of total space available. The lobby has entrances from both 40th and 41st Streets.

Renovated in 1993, the building was acquired in 1997 by TrizecHahn Properties, along with the nearby W. R. Grace Building.

The Seagram Building would've turned out very different if not for Seagram president Bronfman's daughter, herself also an architect, who persuaded her father to hire an architect of world renown and with new ideas. Out of numerous modern masters (Le Corbusier ruled out as "bad influence", Lloyd Wright for his "frontier mentality"), she picked German expatriate Mies van der Rohe, then teaching in Chicago, to design the building.

This 160 m tall building was a further development of Mies's ideas from the 1951 Lake Shore Drive Apartments in Chicago. Working with architect Philip Johnson (who did the interior design of the 74,300 m² building and eventually had also his offices on the 37th floor of the building), Mies started on the design work in 1954.

The plot acquired for the building was on the block earmarked in 1954 for the new Metropolitan Opera development -- eventually the opera was built as a part of the Lincoln Center (image) compound in Upper West Side. The building permit was granted on March 1955 and the building was officially opened on 22 May 1958.

The building is placed to the "rear" portion of the end-of-block site, off the Park Avenue, with no less than one third of the $5 million plot consisting of a stepped-up, pink travertine-clad open plaza with twin fountain pools flanked by trees. The plaza offers no seating and, in fact, Mies wanted the pools to be filled to the brim to prevent people from even sitting on their edge. (Another feature of the building that Mies designed to prevent the inevitable "meddling" of human beings was the omission of window sills and supplying of similar curtains and venetian blinds -- moveable to only three positions -- to every window so that the harmony of curtain wall is retained as much as possible. If only others would be that dictatorial...)

The plan of the building is based on a 8.50 m grid, pursued to unprecedented Miesian accuracy. The elevator core is placed to the back of the building, forming the protruding, windowless back wall of the tower. And because the building preceded the legislation of plaza bonuses (only coming to force as a law in December 1961), its bulk was made possible by using only a quarter of the plot for the tower footprint, thus giving it unlimited height as per the 1916 zoning.

Set on bronze-clad pillars, the 38-storey facade consists of alternating bands of bronze plating and "whisky brown"-tinted glass (the material and colour choices were a result of Bronfman's insistance of having a warmer-toned facade than in the Lake Shore Drive Apts). The building was, notably, the first with floor-to-ceiling windows, making the wall a true curtain of glass, as foreseen by the visionaries of Modern Movement, like Mies himself. Between the windows, there are vertical decorative bronze I-profiled beams attached to the mullions to emphasize the vertical rise of the facade. Van der Rohe personally stated that this was his only building in the United States which met exactly his European standards.

Due to the material choices and custom-made details (largely designed by Philip Johnson) the building became -- per built square meter -- the most expensive skyscraper ever; it cost $36 million, approximately twice as much as normally. In this lavish expenditure, along with the "wasting" of rentable (and thus, taxable) space by providing a large, unbuilt open plaza, lay also the seed for financial loss: the city officials deemed the building excessively prestigious as well as losing the city tax income, and thus imposed on it a taxation value that was nearly double (per square meter) that of other contemporary skyscrapers nearby.

In 1972 Seagram's moved over half of its staff from the building in order to cut costs. Four years later the company itself proposed a landmark status for the building, a request which however was turned down by the Commission due to the young age of the building.

Not in all respects were the proceedings with the city officials failures: the success of the plaza scheme (both as a popular haven and an exhibition space) led to the revision of the zoning regulations to encourage other builders to follow the suit.

The lobby has glass walls with typically "Miesian" thin-framed mullions. It is an extension of the outside plaza with its similar stone cladding on floor, as well as on the elevator bank walls. The ceiling consists of glass tiles. The elevator cars have stainless steel and brass decor.

The adjoining two-roomed Four Seasons Restaurant has its entrance on 52nd Street. The south dining room has French walnut tree panel decor as well as two Richard Lippold brass constructions. The north dining room has landscape decor and a pool in the middle. In the adjoining corridor hangs Picasso's backdrop for "Le Tricorne" ballet (1929).

The building was acquired in 2000 by RFR Holdings, also the owner of the nearby Lever Building, for a sum of $380 million.

The building replaced the Modernist, four-storey Fiberglas House (1948, Skidmore, Owings & Merrill), but it incorporated a new showroom for Fiberglas on the ground floor.

The facade followed the style of the Lever Building with its green glass and aluminium curtain wall. The overall massing of the building, however, differed from its peer: the 26-storey tower is set back from 56th Street, forming a small plaza bordered by a seven-storey entrance wing. Moreover, behind the tower rises a 12-storey through-block wing.

The plaza followed the lead of the new Seagram and Time-Life Buildings, albeit naturally in smaller scale, by featuring a water pool as well as seating.

The entrance lobby extends through the block in the wing at the back of the plot. The 5 m high space has a decor of black Carrara glass and white marble and terrazzo. Joseph Albers provided an incised mural of geometric wireframe patterns on the white lobby wall.

There is 41,800 m² of space for office and retail uses, with many prestigious outlets in the $2,000 per-sq.ft retail spaces.

The building's top floor houses a 740 m² penthouse. In 2000, Steuben Glass vacated the building for 667 Madison Avenue, after 40 years of occupation. Two years later, Walton Street Capital bought the building for $266 million, one of the highest per-sq.ft prices at $611.

The extension, driven by the Rockefeller Center Development Corporation, was to replace the existing low-rises with new office towers along the model set by the Rockefeller Center. Wallace K. Harrison was to head the designing of the buildings and use similar themes in the facade treatment to link the addition to the older skyscrapers east of the avenue.

The construction work of the Time-Life Building was begun modestly with Marilyn Monroe detonating the first dynamite for the excavations in 1957. The building was completed two years later in 1959.

There is 130,000 m² of office space within the building; by acquiring and razing the adjoining Roxy Theater (Walter Ahlschlager, 1927) plot, Rockefeller Center, Inc. could increase the size of the new office tower to exceed the bulk allowed by the single plot's zoning.

At the time of its completion, the building's 48 floors of 2,600 m² were the largest in the world thanks to the column-free interior spaces, with the support columns rising outside the curtain wall, at 8.53 m intervals. Time-Life occupied 21 of the floors itself, with the rest rented out to various tenants.

The 179 m tall building was the tallest slab-formed skyscraper in the city so far, although eventually it became the shortest of the Center Extension skyscrapers. It differs in appearance from the later built "Sixth Avenue Center" skyscrapers, like the next-door Exxon Building, in having less vertical "stripe" elements and more of open glass wall surface on its facade. The exterior column piers are clad in limestone and the walls between consist of green-tinted glass with thin, facade-high aluminium mullions and window-covered mesh spandrels.

The building is set back 25 m from Sixth Avenue and 10 m from 50th Street to create streetside plaza spaces. The plaza is paved with wavy-effect multicolour mosaic -- modelled after similar Copacabana paving in Rio de Janeiro -- of terrazzo which extends to the inside lobby (the original, smoothened, and slippery, surface on th plaza was changed to a coarser one in 2001). A rectangular pool with fountains flanks the avenue side of the tower, with the entrance being from 50th Street. There is a metal sculpture, Cubed Curve (1972) by William Crovello, on the plaza, along with an entrance to the underground concourse and subway.

The walls of the 60 m long and 5 m high lobby make extensive use of patterned stainless steel panelling with gradual hue tinting. The ceiling is of glass with a maroon hue. The lobby has large murals by Fritz Glarner (Relational Painting No.88, 1960) and Joseph Albers (Portals). The 48th floor Hemisphere Club & Tower Suite was a private club and a public nightspot which is now, however, closed.

An eight-story wing borders the building and the plaza to the north. A rooftop pavilion by Gio Ponti with dining and lounge spaces sits atop the middle portion of the wing, next to the office tower.

In 2001 CNN made the decision to build a two-level, twin TV studio facing the city on a space so far occupied by the JP Morgan Chase. The space will be leased by the Time Inc., which itself occupies or leases out the building almost exclusively.

Amid the building's $40 million renovation by Swanke Hayden Connell, the lobby is undergoing a landmark designation process, one of the relatively rare Modernist designations.

It replaced the Produce Exchange Building (arch. George B. Post of the New York World Building, 1884) as an "acceptable" sacrifice to get the Downtown development on the way.

The building occupies most of its large plot, rising in triple setbacks, with only the western portion of the building, facing Bowling Green, rising to the full height of 33 storeys.

Original designs by William Lescaze with Kahn & Jacobs, had a full-plot base with a tower slab placed at right angles with Broadway. In 1957, however, developers Uris hired Emery Roth & Sons to utilize as much as possible of the building rights with their 129,180 m² design.

The completed facade consists of a glass wall of alternate-sized glass panes of a bluish tint, having a similar overall appearance as the glass-walled facades of the Javits Federal Office Building.

In 1998 the Metropolitan Transport Authority leased the building in order to renovate it as its headquarters; six years later, the incomplete work had accumulated a $300 cost overrun in a Mafia-linked scheme.

Founded in 1877 and named after Salmon Chase, President Lincoln's Treasury Secretary, the Chase National merged with the Bank of the Manhattan in 1955 to form the Chase Manhattan Bank.

The building project was first announced in 1955 and involved the creation of a "superblock" comprising two city blocks. The old Chase headquarters building on the other block at 18 Pine Street (Graham, Anderson, Probst & White, 1928) was retained and renovated.

The architects presented two different layouts for the new Chase headquarters: a 52-storey tower with a lower 15-storeyed nearby, as well as the actually realized single 60-storey tower.

The design itself derived much from a previous SOM undertaking, the much smaller Inland Steel Building (1955-58) in Chicago, which pioneered the use of an exterior column system along with a vertically accentuated glass wall facade. The outward appearance of the Chase project was in fact very much just an enlarged version of the Chicago building.

The bank complex spans two city blocks and uses the development rights from both sites. The office tower slab, along with five underground floors, occupying the Liberty Street side block and the adjoining block having the open plaza on top of two floors of banking space. The office tower houses 167,000 m² of space and the floors beneath 56,000 m².

Construction commenced on 28 January 1957 the building was completed by the summer 1960. The construction had cost $121 million, plus the cost of obtaining the city blocks as the building site.

The building is at 247.5 m one of the tallest in Downtown and its facade consists of glass and anodized aluminium plating between the large supporting columns. The glass-walled entrance level of the tower is recessed, with only the columns from the facade above extending to the plaza level. The space between the rectangular support columns is vertically accentuated by a series of narrow aluminium mullions extending to the top of the tower.

Along with the central core for elevators etc., the only vertical supports for the building are the massive columns outside the facade, thus not only freeing the office space from further columns in the working space, but also from the large support columns themelves. The core is offset towards the north side of the tower slab, thus increasing the floor area facing the south wall side.

On the 60th floor is an executive dining room with views all over Lower Manhattan. The extensive interior design is by Davis Allen and Ward Bennett.

The building's elevated plaza was completed in 1962 and was the first one in the Downtown area. It also gave the building its non-street name address -- the pioneer of this sometimes questionable naming habit.

The sculpture work Group of Four Trees (1972) on the plaza is by Jean DuBuffet. There is also the 5-meter deep circular sunken well for Isamu Noguchi's Sunken Garden (1964), a water sculpture garden with basalt rocks imported from Japan (and originally also with goldfish) -- the street-level banking offices open to the well through their glass walls (image 1 2). The bank has also an art collection of its own.

The plans for the building on the full-block site between Madison and Park Avenues were announced in August 1955. The final plans for the skyscraper boasted eleven more storeys than proposed in the first studies in 1952, thus making this 215.5 m tall, 52-storey tower of steel-framed grey glass the tallest new skyscraper in New York City since the RCA Building had been erected in 1933. The Chase Manhattan Bank in Downtown Manhattan was the next tall skyscraper, completed a year later.

As a predecessor of the zoning revision, the massive soaring height of the building was produced by setting it back 17 meters from the Park Avenue side building line and eight from the bordering streets, thus producing a moderately-sized plaza and fulfilling the "light and air" requirement, and by building a 13-storey wing to the Madison side to allow the office tower more height.

Vanderbilt Avenue extends to the mid-block corridor part between the building portions, thus also making the building accessible from four directions. Due to the building's location on top of the Grand Central Terminal railway tracks, the entrance lobby with its elevators is located above the street level, reached from the street by escalators. (For the same reason, the columns of the 6.1 x 12.2 m frame were situated on top of the supports between the tracks, thus removing the need for beamwork to transfer the structural loads to the underground supports.)

The elevated lobby by Bunschaft's co-designers, Natalie de Blois and Jack G. Dunbar has a generous height of eight meters for various exhibitions, but the remoteness of the space from the street has not the least helped its popularity. The street level lobby is a plain open space dominated by the crispy red wall of the tower portion's elevator bank, flanked by the escalators. The paving is of gray granite, with a ceiling of white plastic. All in all, the building incorporates 111,500 m² of space.

The original sidewalk paving of pink terrazzo was removed in 1983, after Union Carbide had sold the building to the Manufacturers Hanover Trust, with the building undergoing also other remodelling. At the southeast corner was added J. Seward Johnson's Taxi (1983), a lifelike bronze statue of a man hailing a taxi.

The building is now the headquarters of the new Chase Manhattan bank, formed in 1996 as a merger of Chase and the Chemical Bank from opposite the street. (Another transaction merged Chase with J.P. Morgan of 60 Wall Street in 2001.)

The relocation of the bank, the largest in the US, from 55 Wall Street in Downtown Manhattan launched a trend that would move several notable bank headquarters and branches to Midtown, especially Park Avenue.

The plot was assembled by the developer Vincent Astor from 1953 onwards, with intentions to replace the residential-use block between 53rd and 54th Streets with an office building. The 46-storey Astor Plaza was announced in April 1955, a month after the Seagram Building got a building permit for the adjacent block to the south. The new building was to be similarly set back from Park Avenue, behind a large plaza, albeit in this case a sunken one. The entrance was to be from a glass cube on the street level, with a glass-walled bridge leading over the "moat" of the sunken plaza. The plaza was to admit access to the commercial space surrounding it below-grade, while the top of the non-setback slab was to house a helipad.

Eventually, the development became not only financially troubled, but also a "holdout" pharmacy prevented proper plot assembly -- only after the First National took over the development, was an agreement reached.

As completed, the 39-storey, 157 m high slab of the building occupies only the half of the block facing Park Avenue, rising straight up with no setbacks. It is flanked from three sides by asymmetrical, setback lower wings that extend all the way to Lexington Avenue.

The glass-aluminium facade is accentuated by a series of vertical mullions between structural piers on the outer walls.

The same year that the Citibank became a subsidiary of the holding company Citicorp in 1974, a skyscraper "annex", the distinctive next-door Citicorp Center, across Lexington Avenue was started.

In 2002, Boston Properties made a winning bid of $1.06 billion on an auction -- the resulting price per sq.ft, $630, is the tallest ever in the Manhattan office market.

The 42-storey building rises on columns from a wrap-around plaza to the height of 166,5 m. The glass-wall facade is characterized by low aluminium spandrels, making it visually appear to consist of more glass than it actually does.

Like the contemporary Union Carbide Building, another SOM design, the Equitable also has a lower mid-block wing, here of 14 storeys. In fact, despite being 50 meters lower than its "black brother", it incorporates more office space -- a total of 130,000 m².

The ground floor of the building incorporates an admission-free gallery, the Paine Webber Art Gallery.

After Equitable changed its operations to the neighbouring west tower of the "Equitable Center" block, the building was taken over by the Paine Webber investment bank in 1985 and the company also posted its illuminated sign on the top of the building.

The 32-storey building consists of two masses, with the base, occupying half of the building's 125,5 m height, extending almost to the property line, topped by a tower portion.

With the straightforward approach by its architect, industrial designer Henry Dreyfus, to the set-back ziggurat type of massing, the building also signalled the end of this style on Park Avenue, followed by "plaza-equipped" towers.

The facade treatment throughout is a grid of pre-cast concrete, framing floor-to-ceiling window panels. The facade is cantilevered on columns, exposing the double-height lobby and a perimeter plaza.

The building's 37,000 m² interior was designed by the bureau of Shreve, Lamb & Harmon.

In 1971 the bank built an addition, called 280 Park Avenue East (arch. Emery Roth & Sons and Oppenheimer, Brady & Lehrecke), behind the headquarters building. The mid-block building differs from its predecessor with its unsetback form and black glass facing.

The building was sold to the Dubai investment firm Istithmar in 2006 as a part of a $2.2 billion deal (possibly) including the 5 Times Square.

The plot on the western blockend between 51st and 52nd Streets was first assembled from 1949 on for the Equitable Life Assurance Society's planned 30-storey speculative office tower -- to be located across the street from the, equally undecided, new company headquarters. In 1955, a 60-storey design by Harrison & Abramovitz was announced, to be the first office tower in the glass-walled International Style on Sixth Avenue -- the Time-Life Building catty-corner was proposed in December 1956 -- although the actual address was to be the better-selling 33 W 55th Street.

The 51st Street portion of the assembled plot was dotted with popular clubs and as one, Toots Shor's, remained as a holdout, the building was designed around it. Nevertheless, Equitable was by now financially preoccupied with its new Sixth Avenue headquarters across the street as well as the next-door Time-Life Building and the company finally abandoned the plan in 1957.

The mega-developer William Zeckendorf took over the plot's fortunes and even managed to buy out Toots Shor and his holdout restaurant with $1.5 million in 1958. He planned a 48-storey, 2,000-room hotel by, yet again, Harrison & Abramovitz on the site. But even though the ground was already broken in spring 1959, financing problems led to an abandonment of the development and Zeckendorf sold the land to the Uris brothers in 1961.

Urises' design on the site was an office tower by Emery Roth & Sons, although the survivors Harrison & Abramovitz were still involved in the design work. The building has a 43-storey tower rising to 173.5 m on the Sixth Avenue side, set-back from the building line behind a plaza and flanked by protruding side wings. A lower, set-back wing takes up the rest of the plot. The building comprises of 158,000 m² of space.

The facades have piers of precast concrete and glass walls with spandrels of black-anodized aluminium and thin mullions.

The Sperry-Rand Corp., the data processor company, occupied eight floors as the first namesake tenant. The renaming of the building -- as the headquarters of the Equitable Life, an AXA subsidiary and the first potential developer on the site -- the AXA Financial Center, was, in the end, a similar twist of irony as the construction of the New York Hilton Hotel by the Urises two blocks to the north -- after the Urises had first deemed the area unsuitable for profitable hotel construction...

The Jamestown Management real estate investment firm is in the process of buying the building after a bidding war with the Equity Office Properties. The $745.5m deal will be the largest in NYC since the WTC deal in 2001.

In 2005, Hudson Waterfront Associates, Donald Trump's Chinese former partners in the Trump Place development, agreed to pay $1.25 billion for the building.

(Jerry Seinfeld : Anywhere in the city?
George Costanza: Anywhere in the city - I'll tell you the best public toilet.
JS: Okay.. Fifty-fourth and Sixth?
GC: Sperry Rand Building. 14th floor, Morgan Apparel. Mention my name - she'll give you the key.
  Seinfeld: "Busboy", 1991)

Originally built as the Americana Hotel, the design stage involved Morris Lapidus, the architect, in a dispute which led to his resignation from working also on the New York Hilton Hotel project due to a "conflict of interest", although the form of this building was derived from his Hilton design.

The 153 m tall twin hotel has a plan, less typical for its age, with diagonal wings set in angles to the middle portion as a bent slab shape. The facade consists of horizontal striping of steel-framed windows and yellow glazed brick facing. Lapidus used the bending slab style earlier in NYC in his 1961 Summit Hotel, on Lexington Avenue.

At the time of its completion, the building was the tallest concrete-framed structure in the city. Its unusual frame system consists of three zones: floors 1 through 5 were supported by steel-concrete composite columns, floors 5 through 29 by concrete sheer walls and 29 to 51 by reinforced concrete columns.

On the north side is a 25-storey wing located above the entrance and the glass-walled lobby. The Seventh Avenue sidewalk has a striped paving that extends around the semicircular rotunda that extrudes from underneath the west end of the slab. The lobby has white marble paving and columns, as well as a domed ceiling with gold leaf decor.

In its original form the hotel incorporated five restaurants and no less than ten ballrooms.

Replacing the Grand Central Terminal Office Building between Grand Central Terminal (link) and the New York Central Building (now Helmsley Building), the plot was to house a skyscraper to utilize the "underdeveloped" site.

A preliminary design by the Roths, a 50-storey north-south-aligned tower slab of aluminium and glass facades (image), was discarded as "too modest" and Walter Gropius and Pietro Belluschi were brought in to join them as design consults.

In February 1959 the new design was presented: Gropius came up with a 59-storey east-west-aligned tower with an oblong octagonal plan. He wanted to reduce the bulk of Roth's slablike structure by cutting the four corners to give the building a sense of continuity. The shape, formed from precast concrete elements, also resembled an aeroplane wing, which suited well the original owner and main tenant, the Pan American Airways (image).

Demolition work on the site began in August 1960 and the building was completed by March 1963 for the cost of $100 million, the first tenants arriving a month later.

The 246.5 m tall building incorporated 223,000 m² of office space (of which Pan Am occupied one-fourth), more than any other commercial office building at the time. The building's large floors, as well as its favourable location and connections have been most lucrative for tenants. There is also the private Sky Club on the 58th floor.

The tower is erected on an eight-storey, granite-clad base which occupies the site between 45th Street and Grand Central Terminal, with the Park Avenue roadways passing on both sides.

The concrete walls of the tower are interrupted by two colonnaded openings on the facade, at 21st and 46th floors, behind which the technical equipment is located.

In 1961 a heliport was opened on the roof, adding another role for the building, as an in-city terminal for NYC airport connections (a realization of a kind of the Empire State Building's "direct arrival" idea). The heliport was finally closed in May 1977, after a helicopter accident that killed four people on the rooftop and a pedestrian on the street.

In the large concourse, connected to Grand Central Terminal (the large volume of pedestrian traffic through the Terminal to and from the high-rise has caused criticism), Gropius used escalators and stairs to accelerate pedestrian movement through the building. The ground floor houses the main concourses, with the 66 elevators of the office tower located in the mezzanine-like second floor lobby, reached by, in all, 14 escalators.

Gropius persuaded the developers to allow bringing in artists to work on the building; the lobbies and concourses contain works by Josef Albers (mural)(removed in 2001), Georgy Kepes (decor) and Richard Lippold (wire construction Flight). In 1987 the lobby system underwent a redecoration by Warren Platner.

Since its completion in 1963, the building has been criticized for its mass blocking the view through Park Avenue and generally dominating the space above Grand Central Terminal and the Helmsley Building, the latter of which Gropius would have rather torn down to make space for a landscaped plaza at the foot of the building.

Pan Am sold the building to the insurance company MetLife in January 1981 for $401 million but the Pan Am logo was replaced with that of Met Life only in 1992.

In April 2005, Met Life sold the building for a record $1.72 billion, almost twice the price the company's other major skyscraper, at 1 Madison Ave., fetched earlier the same week. The buyer was a group led by Tishman Speyer Properties, the developer expanding its Manhattan assets portfolio once more. Met Life continues to keep its headquarters, as well as the facade logos, in place.

The 38-storey building replaced, among other smaller-scale buildings, architect Philip Johnson's old residential house, and was located in the same block as the Lescaze House, built for the Swiss-born architect in the 1930s.

Surrounded by a 600 m² open-air plaza (plus the sidewalks) and an arcade along the street facades, the 12-storey base is topped by a 26-storey tower set on pillars. The curtain wall is of black-anodized aluminium and darkened glass.

The rotating stainless steel sculpture Contrapunto by Beverly Pepper flanks the entrance and the Big Red Swing (Theodore Ceraldi), a red-painted, flat-topped steel shape suspended from the arcade ceiling is located some distance away. The plaza has wooden benches and sidewalk trees -- the latter in direct violation of the strict regulations.

The initial design by the hotel specialist Morris Lapidus (working with Kornblath, Harle & Liebman and Harrison & Abramovitz) was a 38-storey curving slab; after he was relieved of the commission due to working also on the nearby -- and competing -- Americana Hotel, Lapidus used the curve theme on this building.

The 45-storey slab rises on the north side of a four-storey, masonry-clad base extending to the streets. The tower has main facades of blue-tinted glass with metal spandrels, and the vertical window shafts are projecting out from the wall in a series of facets zigzagging through the facade. The ends of the tower are clad in limestone.

There is a driveway underneath the base on the Sixth Avenue side, leading to the hotel entrance. In the western portion of the building there is also a driveway to the hotel carage and its "motor lobby".

The hotel lobby has a pink marble floor and columns and is illuminated by lighting recessed to the edges of the sunken ceiling panels.

The four floors of the base house the hotel meeting spaces as well as the 2,300 m² Grand Ballroom -- the largest in the city -- and promenades, 14,000 m² in all. The 2,200 guest rooms have ceilings 2,4 m high and, due to the zigzagged facades, outer walls forming a V-shaped protrusion. The two top floors house duplex apartments.

Sculptural works within the building include Philip Pavia's sculpture group "Ides of March" in the Sixth Ave. driveway, James Metcalf's cast-iron sculpture in the lobby and Ibram Lassaw's hanging metal sculpture "Elysian Fields" in the promenade area.

In the mid-1990s, the hotel underwent a $90 million renovation and in the 2000s, a $148 million redo.

Located opposite the Union Carbide Building, these two presented the latest trend in skyscraper design, started with the Seagram Building further up the avenue, with their soaring towers set on pillars -- the 277 in fact taking the style of its entrace canopy from the Seagram's.

The buildings employ a similar style of black steel spandrels and soaring white mullions framing the dark-tinted glass -- although here the vertical mullions alternate with narrower black ones, as opposed to their more "dominating" presence on the neighbouring building's facade -- and the building is at 209.5 m of approximately the same size.

The 50-storey building houses 139,400 m² of space within the tower and the set-back additions flanking it on the sides.

The building was acquired in 1980 by the Chemical Bank as its world headquarters, which relocated from the 20 Pine Street in Downtown Manhattan. The 1996 merger with Chase Manhattan marked a move across the street to the ex-Union Carbide Building.

In 1982 the three-storey, glass-walled Chemcourt Atrium by Haines Lundberg Waehler was added to the Park Avenue side of the building, complete with trees, shrubs, plants and a fountain.

The massive building is heavily set-back from Tenth Avenue to a tower on the western side of the plot. The 21-storey building (equivalent of 40 "normal" storeys due to the increased height of each floor) is predominantly white, in concrete and white enamel tiling, with black granite. The building's main bulk is clad into striped walls and the tower's western elevation has twin black stripes rising from the bottom to the top.

Although windowless, the building was completed with large openings at the top for the various antenna equipment, giving it a belfry-like appearance. Later, new openings have been added, as well as the antenna mast to the top.

Like all the other telecom fortresses, this was designed to withstand considerable nuclear blast and fall-out and be self-sufficient for long periods of time.