|Image: Die Externsteine anno 1840. Stahlstich von E. T. Brain nach einem Gemälde von C. Schlickum.|
The region Sauerland belongs, together with the Bergisches Land to the geological unit Rheinisches Schiefergebirge. This area lies right of the river Rhine, between the rivers Sieg and Ruhr, which explains the first part of the name. The highest point in this region is the Kahler Asten in the Naturpark (nature reserve) Rothaargebirge with 841 m asl The size of the Sauerland is west to east 120km and nort to south about 60km.
The rocks of this area are middle and upper Devonian layers, primarily carbonate rocks. Inbetween are some saddles of lower Devonian layer, like the Ordovician schist of the Remscheid Saddle and the Ebbe Saddle. In the Attendorn-Elspe Mulde are upper Karbon.
The whole area is karstified, but the most interresting features are formed at the borders between soluble and non soluble rocks.