Bullicame is a hot spring outside of Viterbo. These spas are free to enter. Dante mentions Bullicame in his “Inferno” and compares its waters with the streams in Hell.
Bullicame Viterbo
Useful information

The hot springs are located inside a protected area. During the wintermonths the area closes at 17:00, in the summer at 18:00. Admission is free.
History and description
On the way to Bullicame, one travels past a number of sights, including multiple caves excavated in the volcanic tuff stone hills. There is also a fountain called the Fontana del Boia because the town’s executioner is said to have lived in the cottage next door and cleaned his tools in it. Another attraction is a small botanical gaden.
Opposite the botanical garden is an open plain covered with a white crust, characterized by the smell of sulfur. This smell comes from the Bullicame, whose waters have been considered medicinal since ancient times (although there were also people who claimed it was the gateway to hell).
The water appears to be boiling, but this is only an impression created by the gases released that cause globs. The temperature of the water does not reach more than 60 degrees.
Opposite the walled well of the Bullicame is a stone column with an inscription by Dante comparing the streams of the Bullicame to those of hell.
The Bullicame supplies the various Terme in the area with hot water.
Other hot water springs near Viterbo are the Terme dei Papi and the waters of Bagnaccio.