A few kilometres from the southern slopes of Monte Amiata, hidden among chestnut and beech forests, there is a place that looks like it belongs on another planet. It is called Bagni di San Filippo, and until a few years ago it was known only to locals. Now it is starting to attract visitors, but it remains far less crowded than Saturnia.
The white rocks, the warm pools flowing through green forest, the silence: this is a place worth the journey.
A white rock canyon in the middle of a Tuscan forest, with hot water steaming between the stones. Bagni di San Filippo is one of the most unusual and least-known places in Tuscany.
The white canyon: what are Bagni di San Filippo
Bagni di San Filippo is a series of thermal springs that emerge on the slopes of Monte Amiata, in the municipality of Castiglione d’Orcia, in the province of Siena. The water temperature at the source exceeds 50 degrees.
What makes the place visually spectacular is not just the hot water: it is the white rock. The water, rich in calcium carbonate, deposits limestone along its entire course, creating formations of brilliant white travertine - stalactites, terraces, natural pools - in the middle of dark green forest.
The most well-known formation is called “La Balena Bianca” (the White Whale): a large travertine concretion that has formed over centuries of mineral deposits and resembles, with a little imagination, the back of a whale emerging from the forest.
The visual effect of the blinding white travertine against the intense green of the vegetation is truly remarkable.
How the white limestone rock forms
The chemical explanation is simple: thermal water, rich in dissolved calcium bicarbonate, loses carbon dioxide when it comes into contact with air. The calcium can no longer remain in solution and precipitates as solid calcium carbonate - travertine.
Over time, layer by layer, the travertine deposit creates those white formations that make Bagni di San Filippo so distinctive. The process is still ongoing: the rocks change shape every year, new concretions form, the pools shift.
This is also why there are no permanent facilities: everything keeps changing.
How to get there and where to park
Bagni di San Filippo is located in the small village of the same name, along the SP61 provincial road connecting Castiglione d’Orcia with the Amiata area.
From Poggibonsi the route is:
- SS2 Via Cassia heading south, as far as San Quirico d’Orcia or Castiglione d’Orcia
- From there, follow signs for Bagni di San Filippo (about 15 km further)
The total distance is about 80 kilometres, approximately 1 hour and 15 minutes.
The car park is a small gravel area near the entrance to the trail. In high season it fills up, but far more slowly than Saturnia; on weekdays it is almost always available. From the car park, the first natural pools are a 10-15 minute walk along a forest path.
The natural pools: how they work
The natural pools at Bagni di San Filippo form spontaneously where water collects in depressions in the travertine. They are not built or maintained: they depend on the flow of the springs.
The pools vary considerably in temperature: some are nearly boiling (near the source, over 45-50°C), others much cooler because the water mixes with the Onzola stream. Before entering, it is essential to test the temperature with your hand.
The most frequented and safest pools are the medium-sized ones, away from the main source, where the water has cooled to around 36-40°C - comfortable and not dangerous.
The travertine bottom is slippery. Water shoes are recommended.
When to go to avoid the crowds
Bagni di San Filippo is far less crowded than Saturnia, but summer weekends are beginning to attract a certain flow of visitors.
The best time is the low season: autumn and winter. In these months, the contrast between snow or cold air and the hot water creates an even more surreal effect. The travertine formations are more visible because the vegetation is less dense.
In summer, weekday mornings are almost always peaceful. August weekends are the most crowded.
Combining Bagni di San Filippo with Bagno Vignoni
Bagno Vignoni and Bagni di San Filippo are about 20 kilometres apart, both in the same area of the southern Val d’Orcia. Combining them in a single day is not only possible but highly recommended.
A possible itinerary from Poggibonsi as a base:
- Morning: visit Bagno Vignoni and the free thermal pools
- Lunch: San Quirico d’Orcia or Castiglione d’Orcia
- Afternoon: Bagni di San Filippo
Or the reverse: start at Bagni di San Filippo early in the morning (when they are almost empty), then move to Bagno Vignoni for the late afternoon, when the light is most beautiful on the piazza pool.
In either case, Hotel Alcide in Poggibonsi is a comfortable base from which to depart and return without stress.
Planning a trip to Tuscany?
Hotel Alcide is in Poggibonsi, in the heart of the Val d’Elsa.
25 km from Siena, 12 from San Gimignano, in the heart of Chianti.
The Ancillotti family has welcomed guests here since 1849.
