
Bagni di Petriolo natural sulphur springs
Free public natural sulphur hot springs (40 °C year-round) where the water cascades through Etruscan-era stone basins into the river Farma at the bottom of a wooded ravine in the Basso Merse nature reserve. The medieval walled hamlet of Petriolo and the 14th-century bath house cling to the cliff above. No facilities, only river-bank rocks; reached by a 500 m gravel path from the SS223 lay-by. Leashed dogs welcome year-round on the river bank and in the cooler river pools (the hot sulphur pools themselves are restricted to humans for hygiene).
Normas: Leashed dogs welcome on river bank and cooler river pools year-round; hot sulphur pools restricted to humans

