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.
Breg (river)
After 46.2 kilometres, the Breg merges with the Brigach in Donaueschingen to form the Danube - ""Brigach und Breg bringen die Donau zuweg"" ("Brigach and Breg bring the Danube together") as the well known rhyme goes. Since the Breg is not only the longest, but also the voluminous river of the Danube with a catchment area of 291.5 km², its source is considered hydrographically as the source of the Danube ("Donauquelle").