Main-Danube Canal, commercialwaterway in the southern German state ofBavaria. Completed in 1992, the canal is 171 km (106 miles) long and runs fromBamberg on theMain River (a tributary of theRhine River) to Kelheim on theDanube River, permitting traffic to flow between theNorth Sea and theBlack Sea. It thus creates a 3,500-km (2,200-mile) waterway that runs through 15 countries and canaccommodate barges carrying up to 2,425 tons of bulk cargo. The canal, one of the largestcivil engineering projects ever undertaken, has a total of 16 locks, each about 190 metres (625 feet) long, 12 metres (40 feet) wide, and up to 30 metres (100 feet) deep. It reaches a height of more than 406 metres (1,332 feet) over theSwabian Alps, south ofNürnberg.

The idea for such a canal dates back to 793, whenCharlemagne, wishing to open a route through the centre ofEurope for his battle fleet, had a channel excavated between two rivers in Bavaria—the Altmühl, a tributary of the Danube, and the Schwäbische Rezat, a tributary of the Main. Heavy rains caused the banks of the channel to collapse, however, and the project was abandoned. In 1837, underLudwig I of Bavaria, work began on a canal between Bamberg and Kelheim, following much the same route as the modern canal. The Ludwig Canal remained in use untilWorld War II, but it was never able to compete with the railways. In 1921 the German government and the state of Bavaria formed a company to build the much larger Main-Danube Canal. Before World War II the company enlarged the locks on the Main River, many locks also havinghydroelectric power stations installed. Most of the construction of the canal itself took place between 1960 and 1992.