There are three artificial waterways built on the Danube : the Danube-Tisa-Danube Canal ( DTD ) in the Banat and Bačka regions ( Vojvodina , northern province of Serbia ) ; the Danube-Black Sea Canal , between Cernavodă and Constanţa ( Romania ) finished in 1984 , shortens the distance to the Black Sea by ; the Rhine -- Main -- Danube Canal is about , finished in 1992 , linking the North Sea to the Black Sea .
There are three artificial waterways built on the Danube : the Danube-Tisa-Danube Canal ( DTD ) in the Banat and Bačka regions ( Vojvodina , in the northern province of Serbia ) ; the 64 km Danube-Black Sea Canal , between Cernavodă and Constanţa ( Romania ) finished in 1984 , shortens the distance to the Black Sea by 400 km ; the Rhine-Main-Danube Canal ( about 171 km ) , finished in 1992 , linking the North Sea to the Black Sea .