There are over 200 recorded lava tubes on Etna besides more than 10 caves along fissures.The lava tubes are tunnels formed where lava had flowed during the eruptions. In Ancient times, they were used as burial and holy places.  Later they were used as niviere.Here is a list of some of the lava caves:

Grotta del Gelo (The Ice cave)
Grotta dei Lamponi (The Raspberry Cave)
Grotta delle Femmine (The women’s cave)
Grotta dei Ladroni (The Thieves cave)
Grotta dei Tre livelli (The Three level cave)
Grotta del Vescovo (The Bishop cave)