The landscape in the area of the Gefale Leeën („fallen stones“) is the result of an enormous rockfall in dolomites of the Middle Triassic (“Muschelkalk”) and sliding processes of the marls below in the valley of the river Sauer near Rosport. A huge amount of large blocks of dolomite lie in front of the rock face, forming a highly irregular surface. A canyon forest has grown on these blocks.