On Mount Etna there are many caves, often created from magma flowing.
The most famous is called "Grotta del gelo" (Ice Cave); it is the southest "glacer" in Europe (inside this cave, you can find ice in every season). My favourite is the "Serracozzo Cave", and for the lazy people Mount Etna provided the "Ladroni Cave" (Thieves cave), really close to the street.
We'll describe only those caves that are easily reachable from non-professional explorers; for all the others we'll spend just a few words.
Enjoy your esploration!!