 The ponds and marshy depressions in the nature reserve, which covers an area of roughly , are fed by the Teufelsloch, a karst spring in the highland forest.They are the remains of an intensive deposition of Werra anhydrites and a representative part of the gypsum karst landscape of the South Harz.The Großes and Kleines Teufelsbad ("Large and Small Devil's Bath") were formed by embankments and have become silted up fishing ponds.