A reformed Benedictine monastic order, whose mother house was the abbey of Cluny in France, founded by Duke William of Aquitaine in 909. Under Abbot Odilo (994–1048) Cluny became the head of a system of dependent “daughter houses” throughout western Europe. In the 11th and 12th centuries Cluny became a spiritual and cultural centre of vast influence; four of its members became popes and it inspired the zealous reforming innovations of Pope Gregory VII from 1073. The monastery church at Cluny was a model for much ecclesiastical building in Europe. By the 13th century the period of greatest achievement was over, as the monastic ideal suffered from too close an involvement with the secular world and too great a share of its wealth and worldly power.