Vienna International Centre

UNO-City / Vienna International Center
The Vienna International Center (VIC, German Internationales Zentrum Wien, often referred to synonymously as UNO-City) is an official headquarters for international organizations in the 22nd district of Vienna, Donaustadt. It was built from 1973 to 1979 by the Republic of Austria and the City of Vienna according to the plans of the Austrian architect Johann Staber. Austria offered the United Nations (UN) such an international center in 1967.
The VIC is the seat of the United Nations Office at Vienna (UNOV) and other international organizations. It is rented to the United Nations at a symbolic rent of 7 euro cents (until 2001: 1 shilling) per year for 99 years. The operating costs are borne by the individual organizations themselves. The institutions of the organizations in the VIC are extraterritorial.
As a further building complex of the UNO-City, the Austria Center Vienna, which was part of the planning from the beginning, was built between 1983 and 1987 next to the International Center VIC. It is Austria's largest congress center where all kinds of events can be held. Around the complex, which has been accessible with the U1 underground line since September 1982, a new district called Donau City was built between the Old Danube and the New Danube by the year 2000.
The construction of the International Center was preceded by a competition that the Argentine architect César Pelli won in 1969. The second and third prizes went to England and Germany, the Austrian Johann Staber was fourth. After revising the four best projects on behalf of the international jury chaired by Roland Rainer, the Kreisky I federal government, an SPÖ minority government, decided in December 1970 to carry out the Staber project, which led to violent protests by the ÖVP opposition and an investigative committee of the National Council, but did not change the decision.
The facility is built on an area of 17 hectares (the land was provided by the City of Vienna) and consists of six office towers with the distinctive Y-shaped floor plan, which are arranged in pairs around a central, round conference building. The layout of the facility is based on an imaginary honeycomb structure (hexagons) in which the buildings are arranged in such a way that they shade each other as little as possible. Staber had originally developed planning variants that went beyond six towers, which would have continued the hexagonal pattern.
The total floor area is approx. 230,000 square meters, with the highest tower (“A”) having 28 floors and a height of 120 meters. The buildings are decorated with works of art by Austrian artists; the sculpture Polis by Joannis Avramidis stands on the plaza.
Text / Source: Wikipedia
de.wikipedia.org/wiki/Vienna_International_Centre

There is also a United Nations headquarters in Vienna: “UNO City”. It is a large building complex.

The Vienna International Center was built from 1973–1979 by the Republic of Austria and the City of Vienna according to the plans of the Austrian architect Johann Staber in the 22nd district of Vienna, Donaustadt, as an official headquarters for international organizations.