Danube
The Danube flows through many cities, including four national capitals (shown below in bold), more than any other river in the world. Ordered from the source to the mouth they are:
The Danube is navigable by ocean ships from the Black Sea to Brăila in Romania and by river ships to Kelheim, Bavaria, Germany; smaller craft can navigate further upstream to Ulm, Württemberg, Germany. About 60 of its tributaries are also navigable.
Spitz, Austria
Spitz an der Donau is a market town in the district of Krems-Land in the Austrian state of Lower Austria, in the midst of the UNESCO World Heritage area Wachau, further down from Willendorf on the left bank of the Danube. The ferry across the Danube here is interesting in that it has no motor or sail: it is powered by rudder set against the river current, anchored to a cable above the river. The ferry carries passengers, bicycles, motorcycles, and automobiles.