Romania ( ; ) is a unitary semi-presidential republic located in Southeastern Europe, bordering the Black Sea, between Bulgaria and Ukraine. It also borders Hungary, Serbia, and Moldova. It covers and has a temperate-continental climate. With its 19.94 million inhabitants, it is the seventh most populous member state of the European Union. Its capital and largest city, Bucharest, is the sixth largest city in the EU. The River Danube, which is Europe's second longest river after the Volga, rises in Germany and flows southeastwards for a distance of 2,857 km, coursing through ten countries before emptying in Romania's Danube Delta. Some of its 1,075 km length bordering the country drains the whole of it. The Carpathian Mountains, with their tallest peak Moldoveanu at , cross Romania from the north to the southwest.