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.
Donau-Ries
In the south the district is crossed by the Danube, which runs from west to east. It is joined by the Lech river coming from the south. North of the river there is a hill chain, the so-called Riesalb connecting the mountain chains of the Swabian Alb in the west and the Frankish Alb in the east. Further north there is the Nördlinger Ries, a huge depression, which is in fact an ancient impact crater, caused by a meteorite some 14.8 million years ago.