Paris was founded and built upon its quarries and hundreds of kilometers of tunnels run under Paris. Open sky quarries were exploited from Antiquity while underground quarries were exploited as from the end of the twelfth century only. In 1813, Imperial decrees forbade the opening of new quarries, and the last Parisian quarry ceased operating just few years after 1860. This interdiction was extended to the entire Seine department on 9 May 1962. Lutetian limestone provided the building stone due to its fine, regular grain. Plaster of Paris made from Barthonien gypsum heated at 120°C was exported worldwide. Senonian chalk was used for the manufacture of lime and whitewash. Ypresian plastic clay was used for bricks and tiles. Today, it is estimated that one tenth of Paris and 3,000 ha of land in the Ile-de-France Region are undermined by ancient quarries. Paris lies on undermined bedrock. Yet, the abandonment of these underground galleries caused serious subsidence problems. The fate of all abandoned cavities is to progressively subside with time. Surface hazards caused by underground disorders can be classified into three categories: (1) Subsidence was frequent in areas where quarries had been dynamited (Buttes Montmartre and Chaumont) or backfilled. (2) Collapses are more dangerous. The most recent, largest and deadliest collapse occurred on 1 June 1961, between Clamart and Issy-les- Moulineaux where the roof fall of an old chalk mine wiped 23 buildings off the map. (3) Sinkholes, whose origin is not always due to quarrying. In gypsum, groundwater can create pockets of dissolution evolving in sinkholes. The most important one was discovered in 1975 below the Gare du Nord train station. These underground disorders had to be identified, consolidated and monitored. A Quarries Inspection Office was created in 1777; it carried out an efficient survey and reinforcement work of cavities. It was therefore decided in 1978 to carry out an early treatment consisting of almost systematic grout injection of residual cavities. Old underground quarries are amongst the many tunnels that constitute the “arteries” and “intestines” of underground Paris and its fans are named “cataphiles”. Several places of interest can be visited. (1) The Catacombs (14th district) of Paris is the most famous site. These former limestone quarries were used from 1785 to 1933 to store insalubrious remains of all the cemeteries of Paris. In the access gallery to the ossuary, the west-east corridor has kept its abandoned pillars and dry stone walls which ensure the stability of old back filling. Until December 2015, before the exit, the tourists had an access to two sinkholes stabilized with cement and painted with black and ochre lines indicating the different geological strata of the cave section. But nowadays, the shortened tour doesn’t allow this opportunity any longer. (2) The Capucins Quarries (where the 14th, 13th and 5th districts meet) are quite different. All the different types of reinforcements used in Paris are displayed here. In addition, a well and a shaft are the most interesting of the site. The Capucins Fountain, is a well located in a gallery and its steps lead to the groundwater level; a water gauge allows the recording of water level variations. Nearby, one service shaft is a former sinkhole converted for staff access: its trapezoidal shape and square section with a height of 14.26 m is remarkable. (3) Ivry-sur-Seine’s district owns two originally reused quarries: Delacroix and Dumesnil. They are open to public access during special events.