Steam rising from natural hot pools

The volcano

Rome is built on a volcano, and here it is

Every lake around Rome is a hole left by an eruption, the stone the city is built of came out of the same eruptions, and in places the ground is still warm.

40 days out13 placesthe nearest is a 37 min drive from Rome

This is the fact that reorganises the whole map. The hills south of Rome are a volcano — one enormous collapsed cone, with the Castelli towns standing on its rim and two lakes in the bottom of it. North of the city there are three more: Bracciano, Vico and Bolsena, each of them a crater full of water.

The rock those eruptions left is tufo, soft enough to cut with hand tools and hard enough to build with. The Etruscans carved their tombs and their sunken roads into it, medieval towns were built out of it and on top of it, and Rome itself is largely made of the stuff.

And it is not entirely finished. Sulphur water comes out of the ground hot at Viterbo, at Tivoli, at Stigliano and in a dozen other places, smelling of eggs and steaming on a cold morning. The Romans built baths on all of them.

A volcano day is a good frame for a first trip out of the city: a lake, a rim town for lunch, and hot water in the afternoon.

Once you have that in your head the rest follows. The dark stone Rome is built of came out of those eruptions. The sunken roads of the Tuscia exist because the ash compacted into a rock soft enough to cut with iron. And the sulphur water people have bathed in since the Etruscans is the heat that has not gone yet.

The best single day for seeing it is the southern one. Stand on the rim at Rocca di Papa or Castel Gandolfo and the whole cone is laid out below you with two lakes in the bottom of it; then drive down to the water, which is deep and cold because it is filling a crater. It is half an hour from the city and it explains more than any museum.

The northern version is the strange one. Bracciano, Vico and Bolsena are three more craters, and the country between them is tufo the whole way — towns the colour of the rock they stand on, tombs cut into the cliffs, cellars going three storeys down, and hot springs coming up in a dozen places around Viterbo.

From the air, all of this becomes obvious in about ninety seconds, which is the honest argument for one of the flights in the catalogue. From the ground it takes a day and a bit of explaining, which is what this page is.

The crater lakes

Albano and Nemi in the southern volcano, Bracciano and Martignano to the north-west, Vico and Bolsena beyond them. Swimming, paddling, sailing and walking round the rims.

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Castel Gandolfo In the old stones

The collegiate church of San Tommaso

A Baroque collegiate church at Castel Gandolfo, built by Gian Lorenzo Bernini.

Free — nothing to pay

Just turn up

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Two kayakers on a calm blue lake On the waterTrending

Kayak on Lake Albano

Three hours paddling across Lake Albano, gear included, children from six up.

€42.40 per person

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Castel Gandolfo In the old stones

The sanctuary of Częstochowa

A Baroque monastery at Castel Gandolfo, from the fourteenth century.

Free — nothing to pay

Just turn up

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Hot water, still coming out of the ground

The part of the volcano that has not cooled. Free open-air pools and built spas, and better in winter than in summer.

Closest to Rome first. Never by who pays us.

An outdoor thermal pool with steam rising off the water In the hot water

Sulphur thermal spa at Tivoli Terme

A day pass to the thermal spa fed by the sulphurous Acque Albule springs on the road between Rome and Tivoli.

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Steam rising from natural hot pools In the hot water

Acque Albule thermal pools

Six pools at a steady 23°C, and the station is right behind the park.

€16 per person

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Terraces of white travertine formed by thermal water In the hot water

Sulphur pools in the Sabina hills

Sulphur pools open till 18:30, and the operator publishes the train to get there.

€12 per person

Books on Terme Sabine di Cretone

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An outdoor thermal pool with steam rising off the water In the hot water

Thermal cures at the Ferentino sulphur spring

The medical side of the Ferentino thermal centre: inhalation cures for the respiratory system, treatments for the locomotor system and rehabilitation, using the sulphurous water…

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An outdoor thermal pool with steam rising off the water In the hot water

Apitherapy in the beech wood

A wellness session in an apiary set inside the beech forest of the Simbruini park, built on apitherapy practices: bee humming, api-aromatherapy and api-sound.

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An outdoor thermal pool with steam rising off the water In the hot water

Full day spa at Stigliano

A full day, 10:00 to 20:00, with access to the whole spa and the outdoor thermal park.

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An outdoor thermal pool with steam rising off the water In the hot water

Morning spa at Stigliano

A five-hour morning slot, 10:00 to 15:00, with the sauna, salt room, infrared rooms, cold chamber, sensory showers, the heated indoor pool, the thermal basin and the outdoor the…

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What people built out of the rock

Tufo towns, sunken Etruscan roads, cellars cut into the hillside and whole underground towns. The soft stone explains all of it.

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Viterbo Under the ground

Underground Viterbo plus the Templar Museum

A one-hour guided route covering about a kilometre of tunnels under Viterbo plus entry to the Templar Museum, with a tasting of local products.

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Viterbo Under the ground

Underground Viterbo: the short tunnel route

A 25-minute walk through about 250 metres of tunnels cut into the tufa under Piazza della Morte, on two levels at three and eight metres below the square, lit by LEDs.

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A caver with a headlamp inside a cave passage Under the ground

Orvieto Underground: the caves under the town

A guided walk through part of the man-made caves dug into the tufa rock under Orvieto, with cisterns, quarries and dovecotes cut into the cliff.

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Where this takes you

Driving time from the middle of Rome, on the road network and without traffic. It tells you whether the day stands up; it is not a timetable.

Getting there

Getting there, the comfortable way

Questions people actually ask

Is there an active volcano near Rome?

Not erupting, no. The Alban Hills volcano south of the city is classed as quiescent rather than extinct, which in practice means hot springs, gas vents and small earthquakes rather than anything to plan around.

Can you swim in the crater lakes?

In several of them, and Bracciano and Bolsena are the popular ones. The card tells you what each operator offers; where a lake has a swimming rule, the people running the day know it.

What is tufo?

Compacted volcanic ash. It cuts like hard cheese when freshly quarried and hardens in the air, which is why this region is full of rock-cut tombs, cellars and entire towns carved rather than built.

Which crater lake is closest to Rome?

Albano, under the papal palace at Castel Gandolfo, about half an hour out. Nemi is the small one next to it and the one with the Roman ships in a museum on its shore (closed for restoration until 7 September 2026 — check before you go).

Is Rome built on a volcano?

The hills immediately south of the city are one — a single large collapsed cone with the Castelli towns on its rim and two lakes in the bottom — and much of Rome is built out of the tufo those eruptions left. The city itself sits on the Tiber plain beside it.

Are the volcanoes near Rome active?

Not erupting. The Alban Hills volcano is classed as quiescent rather than extinct, which in practice means hot springs, gas vents and small earthquakes rather than anything a visitor plans around.

How many crater lakes are there near Rome?

Six within reach: Albano and Nemi in the southern volcano, Bracciano and Martignano to the north-west, and Vico and Bolsena further north. Bolsena is the largest of them and has two islands in it, and Bracciano has no engines allowed on it.

What is tufo and why does it matter?

Compacted volcanic ash. It cuts like hard cheese when it is freshly quarried and hardens in the air, which is why this region is full of rock-cut tombs, sunken roads, cellars and entire towns carved rather than built. It is the single fact that explains most of what you will see north of Rome.

Where can you see the volcanic landscape best?

From the rim at Rocca di Papa or Castel Gandolfo, looking down into the crater with the lakes in it. From a boat on Bolsena, which has two islands in it. Or from the air, where it takes about ninety seconds to become obvious.

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