The geological situation in the eastern part of the Egge is characterised by limestone dating from the Triassic period (“Muschelkalk”). Limestone tends to exhibit karst features, originating in dissolution processes. Rain picks up carbon dioxide in the atmosphere which dissolves in the water and forms a weak carbonic acid solution. This is able to dissolve limestone resulting in the formation of e.g. subterranean cavities – mostly in the layers containing gypsum (Mittlerer Muschelkalk).

The most prominent karst feature of the Egge are sinkholes or dolines – more than 90 are known in the area around Bad Driburg, another 35 further to the west. However, there are no cave systems in the area. Only two small caves occur in the Muschelkalk of the Egge.

A very impressive sinkhole can be visited on the Klusenberg – the short detour is definitely worthwhile. After 700 m please follow the “Eggeweg” (Hermannshöhen), the sinkhole is on the left side of the path – and is well signposted.