Are the San Filippo hot springs free or do you have to pay?

No, access to the natural pools of the White Creek (Fosso Bianco), at Bagni San Filippo, is free: you don't need to buy a ticket to bathe in the stream. However, parking nearby may be paid. Expect around €1.50 to €1.70 per hour depending on the rates displayed on site; check the signs when you arrive, as prices may change. From the parking lot, you generally need to walk 5 to 10 minutes to reach the pools.

Don't confuse it with a thermal pool or a bathhouse, which may charge admission and offer facilities. The Fosso Bianco is a natural site: don't count on lockers or showers on site, and bring a towel as well as shoes that grip on wet and sometimes slippery ground. Access to the pools is free, but local rules may change; respect the signs and any restricted areas, especially around the limestone formations. If you come in high season or on weekends, arrive early: nearby parking spaces are limited.