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.
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").