Danube
Classified as an international waterway, it originates in the town of Donaueschingen, in the Black Forest of Germany, at the confluence of the rivers Brigach and Breg. The Danube then flows southeast for about , passing through four capital cities (Vienna, Bratislava, Budapest and Belgrade) before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.
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.