On the site of an old Roman «fort», this sanctuary was one of the most vibrant focal points of Christianisation in Savoie during the late Middle Ages. Look above all for the crypt where a little rotunda of the Carolingian baptistry with its rough capitalled columns is a moving witness to the early times of the Church. The chancel of the crypt erected in the 15C to support the upper Church houses an entombment from the same era, damaged during the Revolution.