The Stadttheater Ingolstadt is one of the more active regional theatres in Bavaria, with a season of drama, opera, and musical theatre that punches above its weight for a city of its size. The building itself is a modernist 1960s structure, functional rather than beautiful, but the programming quality has historically been strong.
For visitors with an interest in German culture, the theatre is worth checking for events. Performances are in German; the quality of production is generally high. The tourist office can provide a current program. Even if you don't catch a performance, the theatre square is a pleasant part of the old town to walk through in the evening when performances are on and the city feels alive.