Here are some facts about the River Danube. Danube is Europe’s second longest river, after the River Volga. It flows for 1,785 miles from the Black Forest in Germany to the Black Sea. The Danube flows through or flows along the borders of 10 countries: Germany, Austria, Slovakia, Hungary, Serbia, Croatia, Bulgaria, Moldova, Ukraine and […] Almost a third of Danube’s basin area consists of Romanian section and more than one-third of the Danube’s length flows through Romania. The Danube has played a crucial role in political evolution and settlements of southeastern and central Europe. Its banks linking fortresses and castles also work as a crucial waterway between the countries. 1-800-304-9616. *Free airfare on select departures of Grand European Tour, Capitals of Eastern Europe, and European Sojourn, plus select Panama Canal, Hawaii, Mississippi River, Great Lakes and Antarctica itineraries. Glide along the Danube, Rhine, Main, Seine and Elbe Rivers on board a European river cruise with Viking. gvvnf.