The Mouse Tower stands on a small island in the Rhine near Rudesheim and Bingen, one of those compact landmarks that seems made for river legends. Its story is tied to the tale of a cruel bishop devoured by mice, though the tower also had practical roles in river control and signalling.
You view it from the riverbanks or from a boat rather than treating it as an interior visit. It is a classic Middle Rhine sight: castle country, steep vineyards, water traffic, and a little medieval menace folded into the scenery.