Fossa Carolina

48°59′02″N 10°55′18″E / 48.9840°N 10.9216°E / 48.9840; 10.9216

Remaining part of the Fossa Carolina
Map showing the Fossa Carolina canal

The Fossa Carolina (or Karlsgraben in German) was a canal named after Charlemagne in what is today the German state of Bavaria, intended to connect the Swabian Rezat river to the Altmühl river (the Rhine basin to the Danube basin). It was created during the early Middle Ages, long before the Ludwig Canal and the Rhine-Main-Danube Canal. If it was indeed operational, this canal would have been the first to link the Rhine basin to the Danube basin, across the European Watershed. However, contemporary sources are contradictory as to whether it was ever finished or not.