With a length of 2,857 kilometers, the Danube is the second longest river in Europe after the Volga. The name applies from the union of the two source rivers Breg and Brigach, which originate in the Middle Black Forest in the southwest of Baden-Württemberg. As a result, the large basin landscapes northern Alpine foothills and Vienna Basin (upper reaches), the Pannonian lowlands (middle course) and the Romanian lowlands (lower reaches) are crossed. In a vast delta, the Danube flows into the Black Sea in Romania. On their run are the ten states designated as Danubian countries Germany. Austria. Slovakia (Image), Hungary. Serbia and Romania crosses, as well as unilaterally as border river Croatia. Bulgaria. Moldova and the Ukraine touched.