In the Cloup d'Aural, visitors move around and discover the history of the phosphate mines. They lie at the heart of a 30-meter-deep chasm, dug by water more than 50 million years ago. Clay and phosphate then filled the cavity some 30 million years ago. The deposits were unearthed by miners a century ago in their search for phosphate. It was a highly prized natural fertilizer before chemical ones were developed. There is even talk of a phosphate fever at the time. Featured: Thierry Pelissié, curator of the Lot Geological Nature Reserve.