Passau, Germany

Passau sits at the confluence of the Danube, Inn and Ilz rivers, earning the city of roughly 52,000 residents its "Three Rivers City" name. The Romans founded the settlement in 80 AD as Batavis, and its medieval streets still climb above the meeting waters. Saint Stephen's Cathedral, rebuilt in 1698, houses an organ of 17,974 pipes across 233 registers — the largest cathedral organ in the world. The 1219 Old Town Hall displays Bavaria's largest painted historic clocks, while the 14th-century Veste Oberhaus fortress on a 90-metre hill surveys the river junction below.