A river in Central Europe, at 1,780 miles the continent's second longest after the Volga. The Danube flows southeast from Germany past or through Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine to reach the Black Sea.

The Danube originates in the town of Donaueschingen which is in the Black Forest of Germany. Then it flows southeast for 2 872 kilometers, passing through four Central European capitals before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.

Once a long-standing frontier of the Roman Empire.

Danube Course of the Danube in red (Courtesy Wikipedia)