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.
Danube
The International Commission for the Protection of the Danube River (ICPDR) is an organization consisting of 14 member states (Germany, Austria, the Czech Republic, Slovakia, Slovenia, Hungary, Croatia, Bosnia and Herzegovina, Serbia, Bulgaria, Romania, Moldova, Montenegro and Ukraine) and the European Union. The commission, established in 1998, deals with the whole Danube river basin, which includes tributaries and the groundwater resources. Its goal is to implement the Danube River Protection Convention by promoting and coordinating sustainable and equitable water management, including conservation, improvement and rational use of waters and the implementation of the EU Water Framework Directive.