Already in the 15th century, Ugolino da Montecatini, in his Tractatus de Balneis, mentioned the qualities of the water of Petriolo, suggesting at the same time rules to be followed for the treatment: "Other famous baths are those of Petriolo, rich in sulphur and composed of a very coarse substance. They greatly heat, dry, thin down and resolve the humours. They are beneficial to pains in the joints and diseases of the nerves caused by the cold. They are useful in cases of sciatica and for those who have a head full of humours. The treatment consists of keeping the bare head under the water that flows from the lion's mouth. The water must fall first on the front of the head, then on the back, without force, thus drying the humidity in the head. In these cases it usually highly beneficial, since the heating and drying effect lasts for three consecutive years."

The fame of the Baths was further enhanced by illustrious personages, such as the Pope from Pienza, Enea Silvio Piccolomini (Pius II), who visited Petriolo in June 1460, in October 1462 and in May 1464. Near the end of the 18th century the waters of Petriolo were described by the naturalist Giorgio Santi, and in the 19th century by the Sienese historian Giuseppe Giuli. Still today the baths are visited both for water treatments, especially indicated for disorders of the respiratory system and the locomoter system, and for the beauty of the landscape, which offers sights of great interest. A walk through the woods, along the river Farma, leads to a place where hot water can be seen gushing from the rocks.