Diebsturm is one of Feldkirch's surviving medieval towers, built in the 15th century and later used as a prison. The old city walls that once linked it to the rest of the fortifications are gone, but the tower still helps mark the edge of the historic town.
See it while walking between Feldkirch's arcaded streets, gates, and Schattenburg. It is a compact stop, useful for reading the old town as a fortified place.