About AD 611 Bishop Marius transferred his seat from Avenches to Lausanne, and a cathedral church was mentioned in 814. During the early Middle Ages, particularly in the 11th century, the bishop steadily increased his authority over the city. The medieval city was established from the early Middle Ages on the fortified hill of the Cité. The Cité was occupied by the Bishop's Palace (from late 10th century; mostly destroyed), and the later episcopal Château-fort de St Maire (from 1397). From 1481 Lausanne's five independent quarters joined against the bishop. The former bishop's palace (Ancien-Evêché), which has been converted into the Musée Historique de Lausanne.