Frasassi Caves
Once you have had enough of the  pool, you can head for the plunging Frasassi Gorge for a "journey to the centre of the Earth" through the Grotte di Frasassi, one of Italy's largest and most famous complex of caves. An ideal jaunt for a rainy day, and only 20 minutes away.

Some 13 km of limestone caverns have so far been explored and it is reckoned that they may run for up to 35 km.

Equipped with walkways and theatrical lighting, it includes the awesome Grotta Grande del Vento, Europe's largest single cavern, so vast that Milan Cathedral would fit comfortably inside, and some of the most extravagantly fanciful stalagmites and stalactites you are ever likely to see. Even claustrophobics shouldn't find it too challenging. The guided tour lasts for around an hour; dress up warmly as the temperature inside is a constantly low 14 degrees C. It can get quite crowded in high summer, and English tours are bookable.