The Phlegraean Fields are a large area located in the Gulf of Pozzuoli, west of the city of Naples and its gulf. The area has been known since ancient times for its lively volcanic activity. It is an ancient supervolcano. The Phlegraean area includes in particular the municipalities of Naples, Pozzuoli, Quarto, Giugliano in Campania, Bacoli and Monte di Procida.