The Danube River is a river in Central Europe, the continent's second longest after the Volga.
Classified as an international waterway, it originates in the town of Donaueschingen in the Black Forest of Germany at the confluence of the rivers Brigach and Breg. The Danube then flows southeast for 2,872 km (1,785 mi), passing through four Central and Eastern European capitals before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.
Known to history as one of the long-standing frontiers of the Roman Empire, the river passes through or acts as part of the borders of ten countries. Its drainage basin is shared by Romania (28.9%), Hungary (11.7%), Austria (10.3%), Serbia (10.3%), Germany (7.5%), Slovakia (5.8%), Bulgaria (5.2%), Croatia (4.5%), Ukraine (3.8%), and Moldova (1.6%).