The Kleiner Gleichberg (641 m) and the neighbouring Großer Gleichberg (679 m) form a pair of geological twins. Both mountains are basalt cones which are volcanic in origin. The name Steinsburg (867: Steinberg) (stone castle) probably derives from the large stone fields that surround the mountain summit plateau. Johann Wolfgang Goethe recognised the volcanic origin of these stone fields: the basalt of the former volcanic pipe crumbled as a result of erosion to form the blockfields visible today that are a typical indicator of collapsed volcano structures. These basalt blocks were used in Celtic times for the construction of dry stone walls that probably protected the oppidum. A total of three rings of walls were built surround the mountain like city walls. The outermost wall is three kilometres long and encloses an area of 66 hectares. Only a few short sections of these walls have been partially preserved, but the collapsed sections enable the old structure to be made out.