of the fourth century. At first the new diocese was a suffragan of the archdiocese of Vienne; later it became suffragan of Tarentaise.
In 589 the bishop, St. Heliodorus, transferred the see to Sion, leaving the low-lying, flood-prone site of Octodurum, where the Drance joins the Rhone. Though frequently the early bishops were also abbots of Saint-Maurice, the monastic community was jealously watchful that the bishops should not extend their jurisdiction over the abbey. Several of the bishops united both offices: Wilcharius (764-780), previously Archbishop of Vienne, whence he had been driven by the Moors; St. Alteus, who received from the pope a bull of exemption in favor of the monastery (780); Aimo II, son of Count Humbert I of Savoy, who entertained Leo IX at Saint-Maurice in 1049.
The first cathedral is probably from the 6th Century. It was halfway up the hill, where later the church of St. Peter stood, until the 19th Century when that church was demolished.
The fortunes of the city grew when the bishop settled there. In 999, King Rudolph III of Burgundy granted the entire County of Valais to the Bishop, and Sion became the capital of this County. The Prince-Bishop had the rights of high and low justice, the right to his own regalia and to appoint his own vassals. The residents of Sion were ruled by three appointees of the Bishop, the maior, the vice dominus or Viztum and the salterus.
Medieval Sion
As a result of the decline of the feudal social order and thanks to privileges and concessions granted by the bishop, the citizens of Sion had a limited independence in the Middle Ages. A contract between Bishop Kuno and his maior William of Turn from 1179, is seen as the first step in the creation of an independent city government. An agreement between the bishop, the collegiate church of St. Viztums and William of Turn in 1217 is the first written charter of freedom for the city. It includes civil and criminal laws and
