List of tributaries of the Danube
The Danube is Europe's second-longest river. It starts in the Black Forest in Germany as two smaller rivers—the Brigach and the Breg—which join at Donaueschingen, and it is from here that it is known as the Danube, flowing generally eastwards for a distance of some , passing through several Central and Eastern European capitals, before emptying into the Black Sea via the Danube Delta in Romania.
Danube Sinkhole
In the long run, today's upper Danube will probably be redirected entirely into the Radolfzeller Aach, and thus to the Rhine. This would mean that other tributaries that are currently insignificant would become the new headwaters of the Danube. The Danube has experienced a similar stream capture further upstream, during the Würm glaciation, when the "Feldberg-Danube" was captured by the Wutach at the Wutach Gorge near Blumberg.