Source of the Danube
As early as 1847 the following definition can already be found in the "Universallexikon des Großherzogtums Baden" (Universal Lexicon of the Grand Duchy of Baden): “Danube, the biggest river of Germany, rises at the Martinskapelle in a wild and lonely area of the Black Forest, is called Brege at its origin and forms the river Danube in Donaueschingen where it is unified with the Brigach." (German original: „Donau, der größte Fluß Deutschlands, entspringt bei der Martinskapelle in einer wilden und einsamen Gegend des Schwarzwaldes, heißt am Anfang Brege… und bildet erst in Donaueschingen, wo sie sich mit der Brigach vereinigt, die Donau.“)
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.