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–Black Sea Canal
The Danube–Black Sea Canal () is a navigable canal in Romania, which runs from Cernavodă, on the Danube river, to Constanța (southern arm, the main branch), and to Năvodari (northern arm), on the Black Sea. Administrated from Agigea, it is an important part of the European canal system that links the North Sea (through the Rhine–Main–Danube Canal) to the Black Sea. The main branch of the canal, with a length of , which connects the Port of Cernavodă with the Port of Constanța, was built between 1976–1984, while the north branch, known as the Poarta Albă – Midia Năvodari Canal, with a length of , connecting Poarta Albă and Port of Midia, was built between 1983–1987.