This locality is famous for its sulfurous waters with healing powers, recognized even in antiquity and celebrated by writers and poets such as Cicero and Folgore da San Gimignano. Almost certainly known to Etruscans and Romans, Petriolo is mentioned in documents as early as 1130.
Gradually the fame of its waters spread not only to other neighboring regions but throughout much of Italy and beyond, so that it was frequented at all times by illustrious personages. Of the real ancient baths, which were built from four rooms with cross vaults, only one room remains that opens to the outside with round arches resting on octagonal pillars.
