The Collegiate Church was built in the 13th century when Frederick I (Barbarossa) established a Premonstratensian monastery here. In 1511 the order was dissolved and the church was converted into a secular college until 1565 after which the church fell into disrepair. Made of the ubiquitous red sandstone, the first historical reference to it is in 1571, and it is considered to be the most important late gothic church in southwest Germany. It is also known as the birthplace of the "Palatine Union" because here the Lutherans and the reformers in the Palatine joined forces in 1818. Having been damaged badly in the war, the Stiftskirche is now a Protestant parish church. Notice the unusual two-tiered window layout and the steps on the south side that lead to the original level of the monastery. The reformers Calvin and Luther have statues inside.