Historic thermal baths of Viterbo, already used by the Etruscans. Documentations testify to the great importance that the thermal area of ​​Viterbo has held since ancient times, as reported by the writings of Scribonio Largo, writer and doctor of the Emperor Tiberius. In the Middle Ages the thermal baths of Viterbo were a privileged destination for the popes. The spas began to call them "of the Popes" especially after the intervention of the pope Niccolò V. He found so much benefit from the treatments with these waters that in the mid-1400s he had a splendid residence built. The thermal water that flows naturally at 58 ° C is still appreciated for its great therapeutic qualities. They make it suitable for spa therapies. The source feeds a monumental 2,000 m2 swimming pool. The flow of water offers rare muds: the gray lava, used in mud therapy. And the white spring one for aesthetic treatments. 

Il Bagnaccio is a beautiful outdoor thermal park north of Viterbo, once known as "Aquae Passeris". A corner of paradise bordered by the Via Francigena. Inside the Bagnaccio there is an area, near the thermal spring, used for the conservation of the native flora of the Viterbo area. Where there is the possibility to make paths through the botanical garden which also hosts rare species of animals and plants. Like all Viterbo spas they were already known and used in the past. They are earthy, sulphurous and hyperthermal waters. The water flows at a natural temperature of about 63 ° C. 

Bullicame is a source of hot sulphurous water that naturally flows at 58 ° C, located just outside Viterbo, west of the historic city center. The natural spa of Bullicame are the best known thermal and hypothermal springs of Viterbo. They are fed by the large hydrothermal basin, with the lesser known springs, Carletti, San Sisto, Bagnaccio, Zitelle, Piazza d'Armi, and many others. Already at the end of the last century the source has shown a progressive reduction of the water flow, only partially justified by natural reasons. The Bulicame Regio is entitled to Bullicame, a geological formation of the surface of Io, the natural satellite of Jupiter. Like all the other thermal baths in Viterbo, the Bullicame was already known by the Etruscans. There are documents written on Bullicame since the early Middle Ages, as a refreshment and rest point along the Via Francigena. In fact, it is also mentioned in the well-known Itinerary of the Archbishop of Canterbury, Sigerico. The Bullicame is described in the sixth stage, called Mansio, leaving Rome. The locality was called Sce Valentine, as a reminder of the Saints Valentino and Ilario who according to tradition were martyred in the vicinity of the Bullicame.