http://www.ledevoluy.com/fr/activites-loisirs/souterrata-nouveau
This looks fun - the next valley over to me (Dévoluy) in the southern French Alps are opening an underground Via Ferrata next month utilising the sink holes in the area. Could be worth taking a look for those in the area or visiting. Anyone in Ceuse is fairly close to check it out.
I'll report back when I've had a go.
