Rennes les Bains is a very old spa town.
However, there is much more. The town lies in a canyon surrounded by countless sites from which in ancient times has been observed the sun, moon and stars. The many sources has attracted alchemists who have used water and its mineral content in their processing operations.
Just north of town is the mountain Cardou and the two small peaks Blanchefort and Roco Negre. These three peaks forming "accidentally" one Pythagoras triangle - 3-4-5.
This is not a coincidence, as the whole area is steeped in geometric patterns.