A karst region is characterised by the solubility in water of the rock that it is made up of (predominantly limestone). The moulding of the surfaces by the water, the erosion and the presence of grottos, distinguish the karst areas. The surfaces seem tormented, the rock decayed, the phenomena of erosion is imposing.
The Monte Generoso is a karst massif, made up predominantly of limestone flints of the Inferior Lias. Because of the irregular flinty nature of these limestones, the superficial karst phenomena are relatively discreet and irregularly distributed. The deep phenomena are, however, well developed and very old and to a great extent, still unknown.