the aven armand chasm 100 meters underground where the largest known stalagmite in the world is 30 meters high

abyss cavity eerie mysterious mystic mystical spiritual vault earth world drape room hidden show strange passage explore calcite traveling space enigmatic cavern chasm mineral trickle hollow place tunnel stalactite underground destination nature travel cave carbonate stone tourism limestone touristic concretion stalagmite aven armand 100 meters largest high high hures-la-parade lozere france