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.
New Europe Bridge
By April 2012, only one segment in between the bridge decks of PB 9 and PB10 was still missing. After this gap was closed, one could walk halfway across the Danube river. The gap between the bridge decks of pillars PB10 and PB11 was closed during the summer. Despite the low water levels in the Danube river construction continued swiftly, working on the abutment A3, on the Romanian river bank.