Karren near the Zeytintaşi Magarasi, Taurus Mountains, Turkey.
Karren in Gypsum, southern rim of the Harz, Germany.

Karren are minor forms of karst due to solution of rock on its surface. The name Karren is German, or better Austrian, describing a common surface feature in the Austrian and German Alps. In the northern limestone Alps large Karstbare karst areas with impressive Karren exist. Despite this origin the term is used for all forms with this origin both subaerial and subsurface. Lapies is the same thing, the term originates from the French. In English both terms are used equally and synonymously.

Karren are formed when water runs down a rock surface with a slope, dissolving the rock while it runs. Thus karren can be found on any soluble rock like limestone, dolomite or gypsum. Water always takes the direction of the highest gradient, which is commonly described by the term steepest slope. When solution of the surface forms a shallow furrow in this direction, water is flowing into the furrow and through it, deepening it more and more. Finally the whole rock surface is drained through karren.