In the High Middle Ages, when the area was part of the Duchy of Carinthia, the valley belonged to the estates of Millstatt Abbey. From about 1300 the Benedictine monks had large parts of the woodland cleared. The village of Reichenau (possibly derived from , "smoke" referring to slash-and-burn agriculture) was first mentioned in a 1332 deed. A chapel in the neighbouring village of Sankt Lorenzen at a height of (today the highest situated parish church in Carinthia) was already documented in 1216.
