Danube

The Danube is Europe's second-longest river, after Russia's Volga. From the Black Forest to the Black Sea, it runs through much of Central and Southeastern Europe. Breg, the river's longest headstream, rises in Furtwangen im Schwarzwald, while the river bears its name from its source confluence in Donaueschingen onward.

The Danube was once a long-standing Roman Empire frontier and is now the world's longest river, passing through the most countries (10; the Nile is second with 9). The Danube flows southeast for 2,850 km (1,770 mi) from its source in Germany, passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova, and Ukraine before emptying into the Black Sea. Its drainage basin stretches into nine additional countries. The river's largest cities are Vienna, Budapest, Belgrade, and Bratislava, which are all capitals of their respective countries. The Danube basin contains five more capital cities: Bucharest, Sofia, Zagreb, Ljubljana, and Sarajevo. Munich, the capital of Bavaria, is the fourth-largest city in its basin, located on the Isar River.

Fish species found in the Danube river basin include pike, zander, huchen, Wels catfish, burbot, and tench. It also supports a diverse range of carp and sturgeon, as well as salmon and trout. The Danube Delta and the lower portion of the river are home to a few species of euryhaline fish, including European seabass, mullet, and eel.

The Danube has been a traditional trade route in Europe since antiquity. Today, it is navigable for 2,415 km (1,501 mi) of its total length. The Rhine–Main–Danube Canal, which connects the Danube at Kelheim with the Main at Bamberg, connects the Danube to the North Sea. The river also serves as a significant source of hydropower and drinking water. Many European borders, particularly in the Balkans, are also defined by the Danube's flow.

Length: 2,850 km (1,770 mi)