[4] Completed in 1952, the complex consists of several structures, including the Secretariat, Conference, and General Assembly buildings, and the Dag Hammarskjöld Library.

[6][7] These adjunct offices help represent UN interests, facilitate diplomatic activities, and enjoy certain extraterritorial privileges, but do not contain the seats of major organs.

[13][14] While the United Nations had dreamed of constructing an independent city for its new world capital, multiple obstacles soon forced the organization to downsize its plans.

[11] The diminutive site on the East River necessitated a Rockefeller Center–type vertical complex, thus, it was a given that the Secretariat would be housed in a tall office tower.

Wallace K. Harrison was named as Director of Planning, and a Board of Design Consultants was composed of architects, planners and engineers nominated by member governments.

The board consisted of N. D. Bassov of the Soviet Union, Gaston Brunfaut (Belgium), Ernest Cormier (Canada), Le Corbusier (France), Liang Seu-cheng (China), Sven Markelius (Sweden), Oscar Niemeyer (Brazil), Howard Robertson (United Kingdom), Garnet Argyle Soilleux (Australia), and Julio Vilamajó (Uruguay).

Le Corbusier's Project 23 consisted of a large block containing both the Assembly Hall and the Council Chambers near the center of the site with the Secretariat tower emerging as a slab from the south.

Niemeyer's plan was closer to that constructed, with a distinctive General Assembly Building, a long low horizontal block housing the other meeting rooms, and a tall tower for the Secretariat.

Amateur architects submitted designs, and local governments offered park areas, but the determined group of New York City boosters that included Grover Whalen, Thomas J. Watson, and Nelson Rockefeller, coordinated efforts with the Coordinator of Construction, Robert Moses, and Mayor William O'Dwyer, to assemble acceptable interim facilities.

[27] The Manhattan site was ultimately chosen over Philadelphia after John D. Rockefeller Jr., offered to donate $8.5 million to purchase the land along the East River.

Prior to the completion of the current headquarters, the UN used part of a Sperry Gyroscope Company factory in Lake Success, New York, for most of its operations, including the Security Council, between 1946 and 1952.

[16] In April 1948, US President Harry S. Truman requested that Congress approve an interest-free loan of $65 million in order to fund construction.

[41][42] However, the full loan was initially withheld due to a case regarding UN employee Valentin A. Gubitchev and KGB spy Judith Coplon, who had been charged with espionage and were set to go on trial in March 1949.

The House was loath to distribute the full $65 million because the government was concerned that the UN's proposed headquarters would grant diplomatic immunity to the two individuals.

[55] The Secretariat Building was to be completed no later than January 1, 1951, and if the consortium of Fuller, Turner, Slattery, and Walsh exceeded that deadline, they had to pay a minimum penalty of $2,500 per day to the UN.

[73] However, the UN did reject an unusual "model playground" proposal for that site, instead choosing to construct a play area similar to others found around New York City.

[91] The East River-Turtle Bay Fund, a civic group, proposed that the United Nations purchase a 3-acre (1.2 ha) tract located to the south of the headquarters, on the site of the Robert Moses Playground and the Queens–Midtown Tunnel ventilation building between 41st and 42nd Streets.

Ove Arup recommended renovating the UN headquarters over a six-year period, as well as expanding the Secretariat Building, but the UN could not secure funding for the project at the time.

[12] The UN selected Fumihiko Maki to design a building on the Moses site,[110] but the New York State Legislature refused to pass legislation in 2005 that would have allowed these plans to proceed.

[118] A temporary $140 million "North Lawn Building" was built to house the United Nations' "critical operations" while renovations proceeded.

They are equipped with weapons and handcuffs and are sometimes mistaken for New York City Police Department (NYPD) officers due to the agencies' similar uniforms.

[154] Swedish architect Sven Markelius designed the Economic and Social Council chamber, which contained wooden screens on the curved north and south walls, as well as an exposed ceiling.

[162][163] Danish architect Finn Juhl designed the Trusteeship Council chamber, which includes wood screens spanning the north and south walls, as well as baffles and rods on the ceiling.

[172] A quiet room for delegates, designed by Günter Fruhtrunk and Paolo Nestler and donated by the Federal Republic of Germany, contains diagonal paneling.

[189] In October 2011, city and state officials announced an agreement in which the UN would be allowed to build a long-sought new office tower just south of the existing campus on the current Robert Moses Playground, which would be relocated.

[196] Other prominent artworks on the grounds include Peace, a Marc Chagall stained glass window memorializing the death of Dag Hammarskjöld;[197] the Japanese Peace Bell which is rung on the vernal equinox and the opening of each General Assembly session;[198][199] a Chinese ivory carving made in 1974, before the ivory trade was largely banned in 1989;[200] and a Venetian mosaic depicting Norman Rockwell's painting The Golden Rule.

[201] A full-size tapestry copy of Pablo Picasso's Guernica, by Jacqueline de la Baume Dürrbach, is on the wall of the United Nations building at the entrance to the Security Council room.

[204] Two large murals by Brazilian artist Cândido Portinari, entitled Guerra e Paz (War and Peace) are located at the delegates hall.

[224][225] According to architect Aaron Betsky, the United Nations headquarters has often been used to stand for "freedom, justice, and solutions to specific local problems through a grid-like, mirror-like deliberative process".

[223] Due to the headquarters' symbolism, several works of fiction have depicted the building under threat, including the films The Pink Panther Strikes Again (1976), Superman IV: The Quest for Peace (1987), and The Peacemaker (1997).