Historische Senfmühle Cochem is a small working museum devoted to mustard, which sounds slight until you remember that the Mosel has always been as much about cellar doors and table culture as castles. The restored mill uses old stone-grinding equipment, including machinery with roots in the eighteenth and nineteenth centuries, to make cold-ground mustard in limited batches.
Tours are the reason to come: you see the machinery, hear how the seeds are ground without cooking away their oils, and can taste the difference at the end. It is not on the same level as Reichsburg Cochem or the Bundesbank Bunker, but it is a good rainy-hour stop and a very Cochem sort of souvenir if you are already wandering between the old town and the Endert valley.