Fussen itself is at the foot of the Alps. I'm not sure what river runs past the town, but it must be glacier-melt because it is a pale blue. We had hoped to find a hiking trails up into the woods overlooking the castle, but couldn't find a trail map anywhere. The weather really was the pits anyways. Very rainy and dark. But we came to get an eyeful of Fussen's mountains, and that is what we got. Plus, an unexpected gift arching across the sky.
We almost missed the rainbow. I'd gotten a few snapshots of famous Neuschwanstein Castle, and started to walk away. But before we reached the car an excited local ran our way, waving his arms animatedly. "Go back! Go back! Look!" He was making funny arching motions with his hands. We turned and it all made sense.