Which river flows through four capital cities?

Which river flows through four capital cities? The Danube. It passes through Vienna, Bratislava, Budapest and Belgrade—the capitals of Austria, Slovakia, Hungary and Serbia.

From its source region in Germany, the Danube runs roughly 2,850 kilometres eastward through central and southeastern Europe before reaching the Black Sea. No other river flows through as many national capitals. The four cities appear in downstream order as Vienna, Bratislava, Budapest and Belgrade.

The river has long been a transport corridor and political boundary. Its basin links or drains parts of more than a dozen countries, making the Danube a major European waterway as well as a cultural connector. Roman forts, medieval trading centers and modern ports developed along its banks.

A common mix-up is counting regional capitals or cities beside tributaries. Linz, for example, is the capital of Austria's Upper Austria region, but not a national capital. The Danube's famous four-city distinction refers specifically to national capitals situated on the river itself or its navigable urban channel.