The Cloup d'Aural phosphate mines extend within the Causses du Quercy natural park. These deep cavities dug in limestone rock used to be exploited as mines to extract phosphate. This salt served as a natural fertilizer at the start of the 20th century, when chemical substitutes did not yet exist. The mines are also a paleontological encyclopedia of rich and ancient vegetation. The Quercy is actually the only region in the world to allow the study and discovery of climate fauna over more than 30 million years. Featured: Thierry Pelissié, curator of the Lot Geological Nature Reserve.