It is the forth municipality of the region for its population.
Situated on the gulf of the same name, Pozzuoli sits in a volcanic area, the Phlegraean Fields (that is burning fields), which includes a still active volcano, the Solfatara.
A big part of the territory is hilly, including several volcanic craters, among which the Astroni and the one that contains the Averno Lake.
From here, the land descends fairly quickly southward (Gulf of Pozzuoli), while more gradual is the descent westward, where lies a flat area close to the Domitian Coast.
A typical geo seismic phenomenon of this city and the entire area of the Phlegraean Fields is the bradyseism, or the raising or the lowering of the crustal plate due to the increase of the underground pressure. The fast raising of the sea level affected the port in the eighties, which was relocated about 50 meters ahead from the previous position.
It is one of the few cities in the world hosting two Roman Amphitheater, along with Rome, Budapest, Ruins from the Roman Era are numerous, often situated within the residential areas of the city. In particular, is worth to mention the so-called Temple of Apollo, by the Averno Lake.