Carlone is a 10 km long stream which source is 1000 m above sea level, about halfway through Rocche del Casone (or di Colleri) towards the top of Scalette. It flows into Trebbia river close by San Martino di Bobbio, 250 m above sea level.
Carlone thermal waterfall lies in an unspoilt environment close by San Cristoforo. At its foot there is a small pond of thermal water and a source of saline water. Carlone water torrent is thermal because of the high concentration of salt.
In the 11th century the monks from a nearby convent used the salt water of Carlone waterfall and the pond to cure skin diseases. In the middle ages the plague hit Italy, and the monks used this miracle water for baths, mud baths and inhalations to cure all those affected by plague that passed through Bobbio along the Pilgrims’ Way (Via Francigena). Since then, the village was named after San Cristoforo.
The primitive church used to stand next to the cemetery in Chiesa Vecchia. It was abandoned during the Napoleonic period, the remains were the floor, the crypt on a hill near the road that leads to Carlone thermal waterfall. In the village centre there is still the structure that was modified through time of the ancient monastery, nearby the remains of the ancient San Giacomo chapel.