The ruins of this jastestify to the presence around a moor pasturein the 18th century. The word jas, derived from "jacere" meaning "lying" in Latin, refers to these small sheepfolds where the shepherd led his flock to spend the night. The Jas du Blanc was a good representative of these rustic buildings, with a unique sloping roof and walls pierced by small openings to keep the freshness of the stones in summer and the heat of the animals in winter.