The Diocese was founded in Octodurum, now called Martigny in the early 4th century. In 589 the bishop, St. Heliodorus, transferred the see to Sion, as Octodurum was frequently endangered by the inundations of the Rhone and the Drance. Very little is known about the early Bishops and the early churches in Sion. However, in the late 10th century the last King ofUpper BurgundyRudolph III, granted the County of Valais to Bishop Hugo. The combination of spiritual and secular power made the Prince-Bishops the most powerful nobles in the Upper Rhone valley. Sion became the political and religious center of the region. By the 12th century they began building impressive churches and castles in Sion to represent their power and administer their estates. Valère, as the residence of the cathedral chapter in Sion, was one-third of the administrative center of the powerful Diocese of Sion. In the 12th century the Cathedral Notre Dame de Sion was built in the town below Valère hill. Glarier Cathedral became the seat of the Diocese of Sion, while the Prince-Bishop of Sion lived in Tourbillon Castle. The name Valère is first mentioned in 1049 as the site of the cathedral chapter in Sion. The first parts of the church were built between 1100 and 1130 in the Romanesque style. The next construction phase began after 1130 and included the semi-circular apse, the walls and windows and a roof. The third phase saw the church expand and the style changed to the new Gothic style. Between 1235 and 1267 the nave expanded and was flanked with two aisles. During the 13th century, the choir was covered with a Gothic ribbed vault and a rood screen was installed to separate the chancel from the nave. The famous organ was installed around 1430–1435 and other than a modification in the 1700s is essentially unchanged. The murals date from about 1435 as well. The Gothic marble statue of the Madonna with the baby Jesus was added in the 15th century over the high altar. The current choir stalls were added in the mid-17th century. The church obtained the rank of minor basilica at the time of the visit of Pope John Paul II in 1984.
Valère organ
The organ on the west side of the Valère basilica, believed to have been built in 1435, is one of the oldest functioning in the world. It was probably brought to the church by Guillaume de Rarogne, who eventually ended up as the bishop of Sion. Its pipes are arranged to form a rough outline of a church; the larger pipes form two towers, and the smaller ones create a triangular church roof. The organ was modified in the 1700s to play Baroque music, but otherwise remains essentially unchanged. It was renovated in 1954, around the time that another famous early model – the Rysum organ – was repaired.
