The Mosel Valley is a smaller, sleepier version of the Rhine. It too has wonderful castles and fine wines, but far less travelers than the Rhine. The towns are beautiful and fairytail-esque. Perhaps the best castle in all of Germany is to be found in this area - Burg Eltz. You can cruise the Mosel, but the boats are fewer and the trip is slower because you have to go through many locks. There are many cheap places to stay along the Mosel. Below is a video of the Mosel region.