The “Grotte di Frasassi” are the biggest and the most known caves  in Italy. They were discovered in 1971, but they were open only in 1974.
Till now just 13 km have been explored, but it is reckoned that the caves may be 35 km long. Only 1,5 km of this crystalline land is open.
The “Grotta Grande del Vento” is the biggest in Europe and it is so big that the Dome of Miland would fit in it. In addition to this there are the “Abisso Ancona”, the “Sala dei Duecento”, the “Grand Canyon”, the “Sala delle Candeline”, the “Sala Bianca”, the “Sala dell’Orsa” and the “Sala dell’Infinito”.
The guided tour lasts for about an hour. Remember to dress up warmly, as the temperature inside the caves is at 14°C!