Pozzuoli and Campi Flegrei: volcanoes, Roman history and bradyseism west of Naples

The Campi Flegrei are one of the most geologically fascinating and historically rich areas in the Mediterranean, located west of Naples around the town of Pozzuoli. This vast active volcanic caldera — whose Greek name means "burning fields" — is the stage for unique volcanic phenomena: the Solfatara is a walkable crater where the ground is warm to the touch, jets of sulphurous steam hiss from fumaroles and boiling mud pools serve as a constant reminder that we are standing on a living volcano. The phenomenon of bradyseism — the slow rising and sinking of the ground caused by underground magmatic activity — has been documented since Roman times and has shaped the very appearance of the Phlegraean coastline. The Anfiteatro Flavio in Pozzuoli is the third-largest Roman amphitheatre in Italy (after the Colosseum and that of Capua), with an original capacity of 40,000 spectators and an extraordinarily well-preserved underground structure. Lake Averno, surrounded by woodland, was considered by the ancient Romans to be the entrance to Hades — Virgil described it in the Aeneid. The Rione Terra, the oldest part of Pozzuoli, is a unique archaeological park: an entire Roman quarter excavated beneath the modern city. O'Vesuvio B&B in Torre del Greco is the ideal base for exploring the Campi Flegrei, reachable in 50 minutes.

The Solfatara of Pozzuoli: walking on a living volcano

The Solfatara of Pozzuoli is one of the most extraordinary and unique volcanic experiences in the world: an active crater approximately 770 metres across where visitors literally walk on the crust of a volcano. The ground is warm to the touch, in places almost boiling; high-temperature fumaroles emit jets of sulphurous steam and hydrogen sulphide with a characteristic smell of rotten eggs; grey mud pools bubble silently in sheltered corners of the crater. The Romans were already captivated by this place, which they called "Forum Vulcani" — they considered it the workshop of the god Vulcan. The Solfatara is part of the Campi Flegrei volcanic complex, one of the most complex and closely monitored volcanic systems in the world. From O'Vesuvio B&B in Torre del Greco, the Campi Flegrei and the Solfatara are reached in about 50 minutes — a day trip that takes visitors from one volcanic system (Vesuvius, which towers over Torre del Greco) to another (the Campi Flegrei), for an unmatched real-life volcanology experience anywhere in Europe.

Bradyseism: when the ground itself rises and falls

One of the most extraordinary and unsettling geological phenomena of the Campi Flegrei is bradyseism: the slow, inexorable rising or sinking of the ground caused by movements of magma and hydrothermal fluids in the subsurface. In Pozzuoli this phenomenon is documented exceptionally well by the so-called Temple of Serapis (actually an ancient Roman market building), whose columns bear the unmistakable mark of a long period of marine submersion: the perforations of lithophagous molluscs (date mussels) in the columns prove that the entire building was once submerged beneath the sea during the medieval period. Between 1970 and 1984, two bradyseismic crises raised the ground of Pozzuoli by almost two metres within a few years, forcing the evacuation of thousands of residents. Today the phenomenon is monitored in real time by seismic stations and GPS sensors. Visiting Pozzuoli and the Campi Flegrei as a day trip from O'Vesuvio B&B in Torre del Greco allows you to observe this phenomenon first-hand and to understand the volcanic territory that shapes all of Campania, including the landscape visible from our B&B's terrace.

The Anfiteatro Flavio and the ancient underground of Pozzuoli

The Anfiteatro Flavio in Pozzuoli is the third-largest Roman amphitheatre in Italy (after the Colosseum in Rome and the one at Capua), with an original estimated capacity of 20,000 to 40,000 spectators. Built in the Flavian era (1st century AD), it hosted gladiatorial combats, wild beast fights (venationes) and — according to Christian tradition — the martyrdom of San Gennaro, patron saint of Naples. What makes the Pozzuoli amphitheatre extraordinary is the preservation of its underground structure: the hypogea where animals were kept, stage machinery was operated and gladiators waited are still perfectly visitable, creating an eerie and unforgettable atmosphere. In the historic centre of Pozzuoli stands the Rione Terra, one of the most original archaeological experiences in Campania: an entire medieval and Roman quarter, abandoned in the 1970s due to bradyseism, now converted into an underground archaeological park visitable only with a guide. Roman streets, shops and thermal baths remain intact beneath the modern neighbourhood.

Lake Averno and mythology: the gateway to the underworld

Lake Averno, a water-filled volcanic crater set among the green woodland of the Phlegraean fields, is one of the most myth-laden places in all of classical antiquity. The Romans considered it the gateway to the underworld — the kingdom of the dead — owing to its dark waters, the absence of birds (volcanic emissions supposedly killed them), and its position in a basin surrounded by wooded hills that make it resemble an otherworldly place. Virgil in the Aeneid describes Aeneas descending into the realm of the dead through Lake Averno, guided by the Cumaean Sibyl. Cicero, Strabo and Pliny the Elder also wrote of the lake as a boundary between the world of the living and the dead. Augustus and Agrippa in the 1st century BC connected the lake to the nearby Lake Lucrino and to the sea, creating the Portus Julius — an artificial naval base of extraordinary engineering. Today the lake is peaceful and surrounded by footpaths: an evening walk along its shores is an almost meditative experience.

How to explore the Campi Flegrei from Torre del Greco: recommended itinerary

For guests staying at O'Vesuvio B&B in Torre del Greco, a day trip to the Campi Flegrei is one of the most memorable and unusual experiences in Campania. The recommended car route (about 50 minutes from Torre del Greco) suggests a morning visit to the Solfatara (opening 9am), a walk around the Temple of Serapis in Pozzuoli port, a visit to the Anfiteatro Flavio, and an afternoon at Lake Averno with a walk through the woods. Alternatively, for those preferring public transport, Naples Metro Line 2 stops at Pozzuoli in about 40 minutes from Naples Centrale, and the Circumflegrea railway allows you to reach Cumae, an Etruscan-Roman site of extraordinary historical importance. The combined Campi Flegrei-Naples itinerary is feasible in one intensive day. O'Vesuvio B&B recommends visiting the Campi Flegrei on a weekday to avoid weekend crowds. Always check access conditions at the Solfatara before departure — the site has experienced temporary closures in recent years.

Highlights

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  Solfatara: accessible volcanic crater with fumaroles, steam jets and boiling mud pools

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  Bradyseism: a unique geological phenomenon causing the ground of Pozzuoli to rise and sink

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  Anfiteatro Flavio: third largest Roman amphitheatre in Italy with a perfectly preserved underground

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  Lake Averno: legendary mythological entrance to Hades, surrounded by ancient woodland

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  Rione Terra: underground archaeological park with intact Roman streets and shops