Following measures taken in the early 1970s to construct the Danube Relief Channel, UNO-City and an international conference centre, the Austria Center Vienna, were created at the end of the Danube Bridge which lies opposite the Altstadt. In years to come it is planned to deveop a second ultra-modern city centre around UNO-City, to be known as Danube City. UNO-City is leased by the State on a 99-year agreement for a peppercorn rent of one schilling a year to the United Nations, several of whose organizations are housed here. These include the United Nations Industrial Development Organization (UNIDO), the Department of the UN for international Commercial Law (UNCITRAL), the International Atomic Energy Authority (IAEA) and the High Commission for Refugees (UNHCR). Since August 27th 1979 the complex has officially been extraterritorial. The idiosyncratic office-blocks, standing between 54 m (117 ft) and 120 m (395 ft) high, were built between 1973 and 1976 to plans by Joha Staber. The architectural embellishments and the interiors are mainly the work of renowned Austrian artists; on the UNO Plaza Stands “Polis”, a bronze casting by Joannis Avramidis, while inside can be seen pictures by Wolfgang Hollehga, Georg Eisler, Karl Korab, Kurt Regschek, Peter Pongratz and Friedensreich Hundertwasser, with reliefs by Alfred Hrdlicka and Giselbert Hocke.