Title: United Nations University
Content:  The university has several campuses spread over five continents. Its headquarters are located at the UNU Centre in Tokyo, Japan.
Title: United Nations Industrial Development Organization
Content:  UNIDO's headquarters are located at the Vienna International Centre, the UN campus that also hosts the International Atomic Energy Agency, the United Nations Office on Drugs and Crime and the Preparatory Commission for the Comprehensive Test Ban Treaty Organization.
Title: United Nations Interpretation Service
Content: United Nations Headquarters (UNHQ), New York City, New York, U.S. ; United Nations Office at Geneva (UNOG), Switzerland ; United Nations Office at Vienna (UNOV), Austria ; United Nations Office at Nairobi (UNON), Kenya ; United Nations Economic Commission for Africa (UNECA), Addis Ababa ; United Nations Economic and Social Commission for Asia and the Pacific (UNESCAP), Bangkok, Thailand ; United Nations Economic and Social Commission for Western Asia (UNESCWA), Beirut, Lebanon ; United Nations Economic Commission for Latin America and the Caribbean (ECLAC), Santiago, Chile 
Title: March 1946
Content: The United Nations would not be welcome to locate permanently in Greenwich, Connecticut, the UNO's first choice for a site. In a special referendum, the vote was 4,540 to 2,019 against letting the UNO build in Greenwich and its surrounding area. The U.N. headquarters was built instead in New York City. 
Title: United Nations University
Content:   The United Nations University (国際連合大学) (UNU) is the academic and research arm of the United Nations. Headquartered in Shibuya, Tokyo, Japan, with diplomatic status as a U.N. institution, its mission is to help resolve global issues related to human development and welfare through collaborative research and education. In 1969, U.N. Secretary-General U Thant proposed "the establishment of a United Nations university, truly international and devoted to the Charter objectives of peace and progress". Following three annual sessions discussing the matter, the United Nations General Assembly (UNGA) approved the founding of the United Nations University in December 1972. Tokyo was chosen as its main location due to the Japanese government's commitment of $100 million to the UNU endowment fund. Since 2010, UNU has been authorized by the UNGA to grant degrees, offering several master's and doctoral programs. It also facilitates the U.N.'s engagement with academic institutions and policymakers around the world.
Title: UNI Global Union
Content: UNI africa Head office in Abidjan / Johannesburg ; UNI americas Head office in Montevideo ; UNI asia pacific Head office in Singapore ; UNI europa Head office in Brussels 
Title: Headquarters of the United Nations
Content:  The United Nations is headquartered in New York City in a complex designed by a board of architects led by Wallace Harrison and built by the architectural firm Harrison & Abramovitz. The complex has served as the official headquarters of the United Nations since its completion in 1951. It is in the Turtle Bay neighborhood of Manhattan, on 17 to 18 acre of grounds overlooking the East River. Its borders are First Avenue on the west, East 42nd Street to the south, East 48th Street on the north, and the East River to the east. The term Turtle Bay is occasionally 
Title: United Nations
Content:   The United Nations (UN) is an intergovernmental organization aiming to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizing the actions of nations. It is the world's largest and most familiar international organization. The UN is headquartered on international territory in New York City, and has other main offices in Geneva, Nairobi, Vienna, and The Hague. The UN was established after World War II with the aim of preventing future wars, succeeding the rather ineffective League of Nations. On 25 April 1945, 50 governments met in San Francisco for a conference and started drafting the UN Charter, which was adopted on 25 June 1945 and took effect 
Title: United Nations Office at Nairobi
Content: United Nations Environment Programme (UNEP or UN Environment) ; United Nations Human Settlements Programme (UN-Habitat) Food and Agriculture Organization ; International Civil Aviation Organization ; International Labour Organization ; International Maritime Organization ; International Monetary Fund ; Joint United Nations Programme on HIV/AIDS ; United Nations Centre for Regional Development, Africa Office ; UN Women ; United Nations Development Programme ; United Nations Office on Drugs and Crime ; United Nations Educational, Scientific and Cultural Organization ; United Nations High Commission for Refugees ; United Nations Industrial Development Organization ; United Nations Children's Fund ; United Nations Common Air Services ; United Nations Office for the Coordination of Humanitarian Affairs ; United Nations Office for Project Services ; United Nations Political Office for Somalia ; United Nations Population Fund ; World Bank ; World Food Programme ; World Health Organization Headquartered at Nairobi: Presence at Nairobi: UNON also hosts the annual East Africa Model United Nations Conference for secondary school and university students from East Africa.
Title: Headquarters of the United Nations
Content:  The currency in use at the United Nations headquarters' businesses is the U.S. dollar. The UN's stamps are issued in denominations of the U.S. dollar. The complex has a street address of United Nations Headquarters, New York, NY, 10017, United States. For security reasons, all mail sent to this address is sterilized, so items that may be degraded can be sent by courier. The United Nations Postal Administration issues stamps, which must be used on stamped mail sent from the building.

Question: where is the un based?
Answer: New York City.