The Phlegraean Fields is a large volcanic caldera situated to the west of Naples, Italy. It is part of the Campanian volcanic arc, which includes Mount Vesuvius on the east side of Naples. The Phlegraean Fields is monitored by the Vesuvius Observatory. It was declared a regional park in 2003.

Naples is the regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 909,048 within the city's administrative limits as of 2022. Its province-level municipality is the third-most populous metropolitan city in Italy with a population of 3,115,320 residents, and its metropolitan area stretches beyond the boundaries of the city wall for approximately 30 kilometres.