Of what river is XXX a tributary?
Gudenå
Gudenåen flows a total of 176 kilometres (109 mi) from Tinnet Krat in Vejle Municipality, between Nørre Snede and Tørring-Uldum, to Randers Fjord in Randers, on a northward course which takes it through the central parts of Jutland.
Randers Fjord