This church, built between the 12 and the 15C, replaced a convent founded by Louis the German (853). It is definitely worth a visit to see the beautiful stained-glass windows by Chagall (chancel and south transept) and Giacometti (north transept). The remains of the Romanesque cloister include frescoes by Paul Bodmer (1921-1941) and relate the legend of the founding of the abbey.