Roman Catholic Diocese of Sion Roman Catholic Diocese of Sion The Diocese of Sion (, , ) is a Roman Catholic ecclesiastical territory in the canton of Valais, Switzerland. It is the oldest bishopric in the country and one of the oldest north of the Alps. The history of the Bishops of Sion, of the Abbey of St. Maurice of Valais as a whole are inextricably intertwined. The see was established at Octodurum, now called Martigny, the capital of the Roman province of Alpes Poeninae. The first authentically historical bishop was Saint Theodore/Theodolus (died in 391), who was present at the Council of Aquileia in
Burchard of Mount Sion in 1291. According to Jaroslav Folda the account is important not only because of its systematic and yet selective content, but also because of the extent of the "actualia" included in his discussion. Burchard of Mount Sion Frater Burchardus de Monte Sion or Burchard of Mount Sion in English and Burchard de Mont Sion in French also wrongly called Brocard or Bocard, was a German priest, Dominican friar, pilgrim and author probably from Magdeburg in northern Germany, who travelled to the Middle East at the end of the 13th century and wrote his book which under the title "Descriptio Terrae