The Danube flows through several countries.

The Danube is the second longest river in Europe, second only to the Volga River. It originates in the southwest of Germany, flows from west to east through Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania, Moldova and Ukraine, and finally flows into the Black Sea.

The Danube River flows through 10 countries and is the largest river in the world. The tributaries extend to Switzerland, Poland, Italy, Bosnia and Herzegovina, Czech Republic and Slovenia, and finally flow into the Black Sea in Sulina, eastern Romania, with a total length of 2,850 kilometers, a drainage area of 810.7 million square kilometers, an average annual discharge of 6,430 cubic meters per second at the estuary and an average annual runoff of 203 billion cubic meters.

Danube is the river that flows through the most countries in the world. The upper reaches of the Danube River are from Heyuan to Vienna, the middle reaches are from Vienna to the Iron Gate, and the lower reaches are below the Iron Gate. The Danube River has developed shipping, and there are more than 100 docks along the coast, which is the traffic artery of coastal countries. In order to connect other waterways, several canals have been dug, and Germany has built the Rhine-Main-Danube Canal to connect the Danube and the Rhine.

The Danube has played an extremely important role in the settlement, migration and political changes in Central and Southeast Europe. The castles and forts arranged on both sides of it form the dividing line between the great empires; However, its waterway is a commercial channel between countries. In the 20th century, it continued to play the role of trade artery.