This giant limestone cave hollowed out by the Lesse (over 15 km) served as a refuge from the late Neolithic period to the 18C. It has huge concretions (5m-long Minaret stalagmite) and magnificent galleries, such as the crystal Salle des Mystérieus..

This museum displays the results of regional, mainly potholing, digs, such as Neolithic shaped flints, pottery, tools, weapons, fineries including Bronze Age gold jewellery or Iron Age fibulae, a fragment of a diploma belonging to a Roman veteran a..

This audio-visual display enables visitors to see the system's vast majority of caves and tunnels that are only open to experienced potholers (which is 80% of the total).