Campi Flegrei

The Phlegraean Fields (Italian: Campi Flegrei, Italian: [ˈkampi fleˈɡrɛːi]; Neapolitan: Campe Flegree) is a large caldera volcano west of Naples, Italy. It is part of the Campanian volcanic arc, which includes Mount Vesuvius, about 9 km (6 miles) east of Naples. The Phlegraean Fields is monitored by the Vesuvius Observatory. It was declared a regional park in 2003.

The area of the caldera consists of 24 craters and volcanic edifices; most of them lie under the Gulf of Naples. There are effusive gaseous manifestations in the Solfatara crater, which was believed in ancient Rome to be the home of Vulcan, the god of fire. The area features bradyseismic phenomena, which are most evident at the Macellum of Pozzuoli (misidentified as a temple of Serapis): bands of boreholes left by marine molluscs on marble columns show that the level of the site in relation to sea level has varied. Hydrothermal activity can still be observed at Lucrino, Agnano and the town of Pozzuoli.

At present, the Phlegraean Fields area comprises the Naples districts of Agnano and Fuorigrotta, the area of Pozzuoli, Bacoli, Monte di Procida, Quarto, the Phlegraean Islands (Ischia, Procida and Vivara).

The Solfatara crater was accessible on foot until 2017 and contains many steam-emitting fumaroles and over 150 pools (at the last count) of boiling mud. Several subsidiary cones and tuff craters, one filled by Lake Avernus, lie within the caldera.