Rainwater and groundwater containing dissolved chemical compounds, e.g. carbon dioxide, dissolve certain rocks such as limestone, dolomite, gypsum or rock salts. The phenomena associated with the dissolution of rocks, the formation of various types of rock voids and remineralisation in the form of infiltration are called karst after the Karst region in Slovenia. Easily dissolvable gypsum and rock salts are soft and not very resistant rocks, so the life span of rock voids formed in them is short.

The most suitable substrate for the development of caves and other karst phenomena is limestone and, to a lesser extent, dolomite. Both of these rocks occur frequently in nature over large areas. Being dissolved, with numerous cracks and fissures, they are so resistant and hard that they usually do not collapse under the influence of overlying layers.

The exhibition is located in the western part of the staircase and consists of charts describing these karst phenomena, a model of the cave and a rotating model showing surface and underground karst forms.