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.
Danube–Oder Canal
The Holy Roman Emperor Charles IV had envisioned a waterway capable of taking ships from the Oder to the Danube in the 14th century. Records of further plans of such a waterway stem from the 19th century. During the Nazi era, the idea was reborn and the project was put into motion. The project would connect the Oder to the Danube through the Moravian region of the Czech Republic, stretching 320 kilometers and spanning an elevation of 124 meters.