Vienna is the capital and largest city of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million (2.4 million within the metropolitan area,more than 25% of Austria's population), and is by far the largest city in Austria, as well as its cultural, economic, and political centre. It is the 9th-largest city by population in the European Union. Until the beginning of the 20th century it was the largest German speaking city in the world, and before the first world war and the splitting of the Austro-Hungarian empire the city had 2 million inhabitants. Vienna is host to many major international organizations, including the United Nations and OPEC. The city lies in the east of Austria and is close to the borders of the Czech Republic, Slovakia, and Hungary. These regions work together in a European Centrope border region. Along with nearby Bratislava, Vienna forms a metropolitan region with 3 million inhabitants. In 2001, the city centre was designated a UNESCO World Heritage Site.