The Jura blind valleys - or 'reculées' in French - are valleys which sink into the edge of the first karst plateau of the Jura massif. The limestone soils absorbed the surface water and drained it, digging underground networks. Little by little, these underground networks caused collapses materialized by the retreat of the valleys towards the bottom of the plateau, hence the name of ‘reculée’ given to this phenomenon typical of the local geology.