The caves of Mount Cucco (PG)
The Monte Cucco Cave opens inside the mountain of the same name, in the park of Monte Cucco, a massif located in the Umbria-Marche Apennines.

The karst complex is one of the largest in Italy, it extends for approximately 35 km, has a vertical depth of -920 m and has four entrances. It develops entirely on the property of the University of Original Men, located in the municipality of Costacciaro. Since 2009, part of the cave has been open to the public via a tourist-hiking route.

adapted from https://it.wikipedia.org/wiki/Grotta_di_Monte_Cucco

Approfondimenti
 » https://www.grottamontecucco.umbria.it/en/home-grotta-monte-cucco-en/