Monte Cucco is also and above all the Cave Park. There are hundreds of caves – long and extremely long ones, deep and extremely deep ones – in all shapes and sizes and all are of great geological, geomorphologic, speleogenetic, hydrological, faunal, palaeontological and historical interest. As already mentioned, their formation dates from hundreds of thousands of years ago, when extremely hot fluids full of minerals and corrosive acids rose up along the deep fractures in the calcareous rock. In fact, sooner or later, each cave has been a source of thermal or sulphurous water.