Campi Flegrei means "burning fields" — and the name is apt. This supervolcanic area west of Naples has more seismic activity than anywhere else in Italy and a history of dramatic geological upheaval. Highlights include Pozzuoli Old City, the Pozzuoli Amphitheater (one of the largest in the Roman world), the sunken Roman city of Baia, Monte Nuovo (a volcanic cone that appeared overnight in 1538), and the ancient oracle site at Cumae. Take the Metropolitana from Napoli Centrale to Pozzuoli; local buses cover the rest.
Campi Flegrei (Phlegraean Fields)
Supervolcanic landscape with Roman ruins west of Naples