Of the 13km/8mi that have been explored since the cave was discovered in 1953, only 600m/656yd are open to visitors who can walk along galleries linking chambers dug by an underground river and decorated with amazing and varied concretions: draperies up to 6m/20ft long, rimstone pools and columns. Some white stalactites, composed of almost pure calcite, are remarkably bright. Also noteworthy are the prehistoric paintings, believed to date, like the Lascaux paintings, from the early Magdalenian period (around 17000 BC). A video presentation explains the geological phenomena.