This is a *#*#* place, a bit difficult to find as there are no signs, but not a long walk from the road. There is the shelter with a little cave above, with holes in the ground for storage, medieval, and another little chamber. On the left of the shelter is the entrance to a little tunnel with water, leading to another entrance. This leads to much older caves, but you can't get in without permission/key.
There is however a website with lots of information and pictures
http://www.hominides.com/html/lieux/grotte-font-bargeix.php
Something is not right. This message is just to keep things from messing up down the road