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.
Donauinsel
The Donauinsel (Danube Island) is a long, narrow island in central Vienna, Austria, lying between the Danube river and the parallel excavated channel "Neue Donau" ("New Danube"). The island is in length, but is only wide. The New Danube waterway is practically an elongated (swimming) lake, technically a diluvian bed. It has been described as an "autobahn for swimmers", due to its use by people commuting to work.