The degradation of the walls in the Mondmilch Gallery, situated between the Nave and the Chamber of Felines, is the result of a natural alteration process, most often linked to the presence of a bacterium that alters the structure of the calcite. Depending on its level of humidity, its plasticity evolves from a plaster-like state to that of "curdled milk," as it was sometimes referred to by Abbé A. Glory. This phenomenon is common in many caves.