Abbey of Saint-Pierre de Nantua

Syagrius is mentioned in a document issued by Pepin the Short in 757, which granted the monastery the privilege of immunity; this was later confirmed in 817 by Louis the Pious. During this period, Nantua became part of the Benedictine reform promoted by Benedict of Aniane (c. 750–821). In 852, Lothair I placed the monastery under the authority of the bishop of Lyon. In 877, following the death of Charles the Bald during a journey, his body was temporarily buried at Nantua. In 884, his remains were transferred to the abbey of Saint-Denis, near Paris. In 952, Saint-Pierre de Nantua was destroyed during an attack by Hungarian invaders and was subsequently abandoned.

The church of Saint-Pierre was built during the abbacy of Hugh of Semur (1024–1109) at Cluny, replacing an earlier and more modest building consisting of a single nave and an apse. The twelfth-century church had three naves with six bays and a transept, above which opened five apses: three central apses aligned with the naves and two lateral apses opening onto the transept. This chevet was extensively remodelled in the fifteenth century. At the western end stands the main portal, which once featured an important sculptural decoration, badly damaged during the Revolution. The other buildings of the priory have disappeared or have been concealed by later constructions.