St. Petri Dom
Construction of the cathedral began in the mid-11th century. Its two prominent towers, one of which can be climbed, are Gothic, but in the late 1800s the cathedral was restored in the Romanesque style. It served as the seat of an archbishop until the Reformation turned the cathedral Protestant. It has a small museum and five functioning organs. On Saturdays at 12:30 there are guided tours of the cathedral.