Maars are formed by steam explosions when groundwater comes into contact with hot magma, during a single explosive event. Typically, a maar is surrounded by a ring of ejected material. A distinction is made between a maar lake and a dry maar.

The nearly horizontal, wavy rock layers that are clearly visible here, were formed under the influence of a maar lake. These layers are exceptionally rich in sedimentary inclusions. A heavier (denser) upper layer exerted pressure on a lighter (less dense) lower layer. This could have been the cause of the significant deformation of the layers.

Building material quarried here proved to be of significantly lower quality compared to the rest of the fortress hill. This is due to the more porous structure of the rock found in the Maar Lake.