The ridge at Rouenceau into which the grottes are builtThe grottes near Charnizay were built as refuges in the period between the Norman Invasion of the 10th century and the Feudal Wars about a hundred years later, when the Normans started beating up on each other (and the local peasants) rather than just the local peasants. They are built into a low cliff face about a kilometre from the village itself, and consist of a number of passages opening up off a central chamber. We didn't explore inside, because we forgot the torch. (You have it right - a caving expedition with no lighting is not our cleverest idea).
Almost hidden in the undergrowth