Rhine–Main–Danube Canal

The Rhine–Main–Danube Canal , in Bavaria, Germany, connects the Main and the Danube rivers across the European Watershed, running from Bamberg via Nuremberg to Kelheim. The canal connects the North Sea and Atlantic Ocean to the Black Sea, providing a navigable artery between the Rhine delta , and the Danube Delta in south-eastern Romania and south-western Ukraine . The present canal was completed in 1992 and is 171 kilometres long.
Projects for connecting the Danube and Rhine basins by canal have a long history. In 793, the Emperor Charlemagne ordered the construction of a canal—the Fossa Carolina, or Karlsgraben—connecting the Schwäbische Rezat, a tributary of the Rednitz, to the Altmühl near Treuchtlingen. Between 1836 and 1846 the Ludwig Canal, or Ludwigskanal, named for King Ludwig I of Bavaria, was built between Bamberg and Kelheim. This canal had a narrow channel, with many locks, and a shortage of water in the peak section, so the operation of the waterway soon became uneconomic — especially given the rapidly advancing construction of the railway network in the southern German countryside. The canal finally was abandoned in 1950, after a decision was made to not repair damage it had suffered during World War II.

Wikipedia