The Danube flows through or along the boundaries of more national capitals than any other river.
It passes through four capital cities: Vienna in Austria, Bratislava in Slovakia, Budapest in Hungary, and Belgrade in Serbia. The river rises in Germany's Black Forest and travels about 2,850 kilometres before reaching the Black Sea.
The Danube basin spans 19 countries, more than any other river basin. Its importance has made it a major route for trade, migration, and cultural exchange since antiquity. The Rhine is also a significant European waterway, but it does not pass through as many national capitals. The Danube's delta is shared mainly by Romania and Ukraine.