The '''Danube''' , or '''Ister'''<ref>[[Herodotus]], ''Histories'', 5.9.1</ref> is the second longest river in [[Europe]] (the longest being the [[Volga]], in [[Russia]]). It rises in two sources: the [[Brege]] and the [[Brigach]] rivers, both in the [[Black Forest]] in the South-West of [[Germany]]. It flows about 2,850 km to the [[Black Sea]].
Its path takes it through or past Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania, Ukraine, and Moldova. It often forms the border between countries: between [[Slovakia]] and [[Hungary]] from Bratislava to Szob, the northern two thirds of the Croatia-Serbia border, part of the Serbia-Romania border, and most of the Romania-Bulgaria border. It also flows through a number of cities, three of which are capitals: [[Vienna]] (Austria), [[Bratislava]] (Slovakia), and [[Budapest]] (Hungary).