Fosso Bianco (Bagni San Filippo)

What to expect

Fosso Bianco is a small stream in the woods just below Bagni San Filippo, a hamlet of Castiglione d’Orcia on the lower slopes of Monte Amiata in southern Tuscany. Several hot springs join it, and the calcium carbonate they carry has coated the streambed in white travertine. The deposits form ledges, small waterfalls and natural pools where you can sit in warm water in the shade of the woods.

The best-known feature is the Balena Bianca (white whale), a large white formation with ridged edges that people compare to a whale’s mouth or baleen. Water spills over it from a nearby spring. Another formation nearby is nicknamed the glacier. The water itself looks milky blue or white in summer and can turn greenish-brown in winter after rain, when the stream carries more runoff.

The hottest spring, near the Balena Bianca, comes out at about 118°F48°C. The water cools as it runs down the stream, so the pools at the top are the warmest and those lower down are milder and often quieter. Some pools hold soft grey mud, which visitors smear on their skin.

This is a wild site with no staff and no facilities. There are no changing rooms, lockers, toilets, food stands or bins along the stream. Bring a towel, water shoes, food, water and a bag for your rubbish.

Rules and etiquette

The site is free and has no gate, but there are rules, and the area gets heavy use.

• Do not touch, climb on or bathe at the Balena Bianca. Visit Tuscany states the ban plainly: the formation is fragile, and touching it, walking on it or bathing right next to it is prohibited. Skin oils and feet wear away the travertine. Use the other pools along the stream.
• Stay off the formations in general. The flow and the shape of the pools change often, and new deposits are thin and easy to break.
• Swimsuits. This is a busy public place in Italy, used by families. Keep your suit on.
• No soap or shampoo in the pools.
• Carry everything out. Litter has been a long-running problem here. There are no bins on the path.
• Respect the village. Park only where signs allow, keep noise down at night, and use the village bars and toilets as a customer.

The comune has wrestled with overcrowding. In 2023 it tried a small paid access wristband (about €2, according to greenMe). In 2024 it hired a traffic warden for the summer to manage parking and the flow of visitors toward the Balena Bianca, and the council set up a special commission on the Fosso Bianco area, while opposition councillors pushed for the comune to buy the whole site. As of August 2026, entry is listed as free again. Check for new rules before a summer visit.

Getting there

Bagni San Filippo sits just off the SS2 Via Cassia, between San Quirico d’Orcia and Radicofani.

• From Siena: about 68 km (42 miles), roughly 1.5 hours, south on the SS2 Cassia.
• From Florence: about 150 km (93 miles), roughly 2 hours.
• From Rome: about 188 km (117 miles), roughly 2.5 hours.
• From San Quirico d’Orcia: about 21 km (13 miles), roughly 25 minutes.

From the village, the way in is a white gravel road at the entrance to the upper part of the village, then a short path through the woods down to the stream. Most people take 5 to 10 minutes. The path is uneven, can be muddy, and is not accessible to wheelchair users, according to the comune.

Parking is the hard part. Parking along Via del Fosso Bianco and in the village lots is paid, about €1.70 an hour, €5 for three hours or €10 for a day according to a 2024 article. A few free spaces exist along the main road outside the village, but they fill early and mean a walk beside traffic. On summer weekends the village can be full by mid-morning.

Buses are run by Autolinee Toscane, but services to Bagni San Filippo are sparse. A car is the realistic option.

When to go

Fosso Bianco is open all year, day and night, and the water is warm enough to bathe even in winter.

Weekdays and early mornings are much quieter. Social media made the Balena Bianca famous, and August and holiday weekends are crowded.

Late autumn and winter are good for a soak, when steam rises in the cold air. The path is muddier, and heavy rain can change the stream’s flow and temperature.

Summer is warm and busy. The water is still hot, so mornings and evenings are more pleasant than midday.

Where to stay nearby

There is no camping at the stream.

• Bagni San Filippo has a few hotels and guesthouses within walking distance of the path.
• Abbadia San Salvatore, about 10 km (6 miles) away on Monte Amiata, has more hotels and restaurants.
• San Quirico d’Orcia and Bagno Vignoni, about 20 km (12 miles) north, are good bases for the rest of the Val d’Orcia.

History

The springs were known in Roman times. The village is named after San Filippo Benizi, a friar who, by tradition, hid in a cave here in the 13th century to avoid being made pope; the Grotta di San Filippo Benizi, carved into the travertine, is still a place of pilgrimage near the village. Cosimo I de’ Medici had the baths rebuilt in 1566. In the 1700s the architect Leonardo De Vegni used the springs’ mineral deposits to cast decorative reliefs. The site has appeared several times in the FAI’s Luoghi del Cuore list of places Italians want protected.

Safety notes

• Hot water near the source: the spring is about 118°F48°C. Test pools by hand and do not sit directly under the hottest flows.
• Slippery rock: wet travertine is slick. Wear water shoes.
• Untreated water: keep your head above the water and do not drink it.
• Valuables: there are no lockers. Leave valuables at home, not in the car.

Nearby stops worth adding

Bagno Vignoni, about 17 km (10 miles) north, has free hot channels below its medieval village square. About 30 km (19 miles) east, Fonteverde at San Casciano dei Bagni is a Medici-era thermal resort with day spa packages. For another free Tuscan soak, Cascate del Mulino at Saturnia is about 57 km (35 miles) to the south-west.