Vienna is the main and the largest city in Austria, divided into 23 districts. The city lies on the banks of the Danube, 40 km from the border with Slovakia and the Slovak capital Bratislava. Vienna has about 1.6 million inhabitants (one-fifth of the Austrian population). Symbol of Vienna is St. Stephen’s Cathedral, the seat of the Archbishop of Vienna, and a patron saint of the city is St. Leopold. The headquarters of several international organizations are located in Vienna: OPEC (Organization of Petroleum Exporting Countries), IAEA (International Atomic Energy Agency) and UNIDO (Industrial Development Organization of the United Nations).