This is perhaps the only place in the world where one can walk on a crater of a dormant volcano. A must see place when visiting the Bay of Naples, and a place very few North Americans have heard of. Public transportation is very convenient. From Napoli, take the Metropolitana Line 2 to the end of the line in Pozzouli, then walk up the hill for 15 minutes. The enterance is on the left. Pozzouli is a safe place to walk in the daytime.