A cave at the entrance to Panex, in the Prealps, called the Creux d'Enfer or Grotte aux Fées.
The Creux d'Enfer is a huge sinkhole which is about 150 metres across at the top with wooded slopes varying in steepness depending on what side you're on. You walk down to it across quite a steeply sloping meadow to a huge arch of black marble rock comprising a cave which you enter through a large opening.
As legend would have it, fairies used to live in this cave and went into the surrounding fields to protect the crops and tell the peasants the best days to work in the fields. Their echoing cries were heard from the top of the mountains and in the woods, from Panex to Bretaye, via Les Ecovets. It's said that the farmers who listened to their advice always had a good harvest.