The Rhine-Main-Danube Canal (in German known as the Main-Donau-Kanal) is a canal that joins up the three rivers Rhine, Main and Danube so that boats can travel from one to the other. It is in Bavaria in the south of Germany. It goes from Bamberg, past Nuremberg, to Regensburg. It was finished in 1992. Boats can now travel from Rotterdam in the Netherlands all the way to the Black Sea. The canal is 171km (106 miles) long. 