Lazio is the area around Rome. It has two geologically and geographically different parts.
Around Rome, the flat lands of the river Tiber, the coastal plains, and the hills are rather young. The hills were formed by a series of gigantic volcanic eruptions around the Albani Hills. The most obvious signs of this volcanism are the circular crater lakes Lago di Boldesna and Lago di Bracciano, and the numerous spas in this area. There are no natural caves in this are, but the long history of Rome is the reason for a vast system of underground structures. There are numerous underground sites of any imaginable category, which are open to the public.
The second, much older part is a chain of calciferous mountains, running roughly parallel to the main Apennine range, called Appennino Abbruzzese. This area is very interesting for cavers, as the limestone is karstified. The caves of this area lie all in this area.
Grotta dell’Arco di Bellegra
Calcata Cave Houses
Cisternone Romano
Grotta di Collepardo
Pozzo del Diavolo
Grotte di Falvaterra
Tomba Francois
La Grotta Dei Germogli
Chiesa della Madonna del Parto
Pozzo del Merro
Grotta di Pastena
Grotte di Pilato
Eremo di Poggio Conte
Re Tarquinio
Dolina del Revotano
Eremo di San Cataldo
Eremo di San Leonardo
Grotta di San Michele Arcangelo, Monte San Giovanni in Sabina
Pozzo Santullo
Sacro Speco
Bunker Soratte
Grotte di Val de’ Varri
Roma
Grottino del Campidoglio
Catacombs of Rome
Cloaca Maxima
Colosseum
Labirinto di Roma
Labirinto Casilino
Lupercale
Mithraeum San Clemente
Neronian Cryptoporticus
Mitreo di Palazzo Barberini
Parco Villa Gregoriana
Underground Basilica of Porta Maggiore
Santa Prisca Mithraeum
Mitreo delle Terme del Mitra
Sacre Grotte Vaticane
Vicus Caprarius
Villa Torlonia