An island that lies off the coast of western France just south of the mouth of the Loire, first colonized by Philibert monks in the 6th-7th centuries. The monastery became an important producer of salt during Carolingian times. From 842, the Vikings raided the island repeatedly, forcing the monks to flee inland with the remains of St. Philibert. There they constructed the church of St. Philibert de Grandieu, one of the finest examples of French 9th-century architecture.