seven years. Up to 1083 it was an imperial monastery, and its discipline often suffered severely on account of imperial interference in the election of abbots. In the beginning of the Conflict of Investitures it sided with the emperor, until forced to submit to the pope by Matilda of Canossa in 1083. It finally declared itself openly for the pope in 1111 when Placidus of Nonantola wrote his De honore Ecclesiæ, a defence of the papal position during the Conflict of Investitures. From the 13th century onwards the monastery decayed badly; the final decline began in 1419, when it came under the jurisdiction of commendatory abbots. In 1514 the abbey came into the possession of the Cistercians, but continued to decline until it was finally suppressed by Clement XIII in 1768. On 23 January 1821 Pius VII restored the monastery, with the provision that its prelature nullius should belong to the Archbishopric of Modena. Main sights Nonantola contains several remains from the Middle Ages. These include the two towers called dei Modenesi and dei Bolognesi, and the Pieve of S. Michael Archangel (9th century). The main monument, however, is the renowned abbey of San Sylvester Romanesque basilica, erected from the 8th century onwards. In the years 1913–17 it was restored to its original early 12th-century condition. References Cities and towns in Emilia-Romagna