Socialist Federal Republic of Yugoslavia
Regarding rivers, the Danube was navigable throughout its entire course in Yugoslavia, linking the ports of Belgrade, Novi Sad, and Vukovar with Central Europe and the Black sea. Long stretches of rivers Sava, Drava and Tisza were also navigable.
Havel
The Havel is navigable from the Mecklenburg Lake District to its confluence with the Elbe. Whilst its upper reaches carry little other than leisure traffic, further downstream it provides an important link in the German commercial waterway network, carrying traffic from the Rhine and the North Sea to Berlin and Poland.