Vienna is the seat of several international organisations, institutions and companies. Various special diplomatic meetings have been held in Vienna in the latter half of the 20th century.
Along with New York, Geneva and Nairobi, Vienna is one of the four headquarters of the United Nations. The Vienna International Centre (VIC), commonly known as “UNO City”, was designed by Austrian architect Johann Staber. Opened on 23 August 1979, it has been rented to the United Nations for 99 years at a symbolic rate of 1 Austrian Schilling annually.

More than 4,000 employees from over a 100 countries work for the Vienna-based organizations. About a third of them are Austrians. Some €22 million in annual operations costs are borne by the Organizations themselves. The VIC also pumps about €360 million annually into the Austrian economy in the form of administrative expenses, the purchase of office equipment and supplies, and spending by staff and conference delegates.

Numerous international conferences and meetings are held annually at the Vienna International Centre. Events of a much larger dimension are held in the adjacent Austria Center. Among others the following UN Agencies have their headquarters in Vienna:

International Atomic Energy Agency (IAEA)
United Nations Office on Drugs and Crime (UNODC)
United Nations Industrial Development Organization (UNIDO)
United Nations Commission on International Trade Law’s secretariat (UNCITRAL)
United Nations Office for Outer Space Affairs (UNOOSA)

Besides other major international organisations have their headquarters in Vienna, like
the Organization of Petroleum Exporting Countries (OPEC), or
Organization for Security and Co-operation in Europe (OSCE)