The Danube (English pronunciation: /ˈdænjuːb/ dan-yoob) is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway.
The river originates in the Black Forest mountain range in Germany as the much smaller Brigach and Breg rivers which join at the German town of Donaueschingen. After that it is known as the Danube and flows southeastward for a distance of some 2,872 km (1,785 mi), passing through four Central and Eastern European capitals, before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.
Known to history as one of the long-standing frontiers of the Roman Empire, the river flows through or acts as part of the borders of ten countries: Germany (7.5%), Austria (10.3%), Slovakia (5.8%), Hungary (11.7%), Croatia (4.5%), Serbia (10.3%), Bulgaria (5.2%), Moldova (1.6%), Ukraine (3.8%) and Romania (28.9%). (The percentages reflect the proportion of the total Danube drainage basin area).