An hour or so down the river from Cologne, we jumped off at Koblenz, and failed to find a luggage store that worked. So we did a 5km walk along the Rhine and through the old town with all of our luggage in tow!
Koblenz is where the Rhine and Mosel rivers meet under the shadow of a huge fortress on the opposite bank. It was a quaint little stop, clearly popular with river cruises, but relatively sleepy and we were glad it was only a brief stop before we journeyed on to Mainz.