Vienna is the capital of Austria, and also one of the nine states of Austria. Vienna is Austria's primary city; with a population of about 1.7 million (2.3 million within the metropolitan area), it is by far the largest city in Austria as well as its cultural, economic and political centre. It is the 10th largest city by population in the European Union and is identified having the 3rd highest quality of living. The United Nations has offices there, as does OPEC. The Vienna International Centre near the Danube also hosts important international offices including the International Atomic Energy Agency. Vienna lies in the very east of Austria and is close to the Czech Republic, Slovakia and Hungary. In 2001, the city centre was designated a UNESCO World Heritage Site and an Economist Intelligence Unit study of 127 world cities ranked it first equal with Vancouver for the quality of life.