The Johanniskirche, dedicated to John the Baptist, is the larger of the two medieval churches in the centre, with two stone towers — one of which is climbable in summer (from a side entrance, modest fee) and gives the best view over the Altstadt and the surrounding forests. The interior is austere late-Gothic, much restored after war damage.
Students live in the north tower as a long-running tradition: it has had a 'tower keeper' apartment up there for centuries, currently let to a small group of students who are expected to ring the bells for special occasions.