I leave soon for some casual biking from Passau to Vienna along the Danube, then another trip around Lake Constance. I'd be interested in finding some things of visual interest along the way that would be fun to photograph, meaning pretty free (moving around, not price) access, not packed with people, and preferably exuding history. Suggestions? PS We'll have one full day each in Munich, Passau, Vienna and Konstanz.