The Fontaine de Vaucluse () is a karst spring in the commune of Fontaine-de-Vaucluse, France. It is the largest karst spring in metropolitan France by flow and fifth largest in the world, with annual output of of water. The spring is the prime example in hydrogeology of a "Vaucluse spring". It is the source of the Sorgue. Geography Location The Fontaine de Vaucluse is in the commune of Fontaine-de-Vaucluse in the department of Vaucluse. The commune was formerly called "Vaucluse", but being in a department with the same name caused confusion, so the commune was renamed "Fontaine-de-Vaucluse", after the spring. Origin of the name The village in which the spring is located was called "Vallis Clausa" ("closed valley") in Latin because of its topographical position. This in time became "Vaucluse", from which the spring takes its name. The name in the Provençal dialect is "Fònt de Vauclusa", the spring of the closed valley. The word font has two meanings in Provençal, "fountain" and "spring". Here it designates a spring and not a fountain. Geology The Fontaine de Vaucluse was formed after the Messinian salinity crisis, during the latter part of the Messinian age of the Miocene epoch, from 5.96 to 5.33 Ma (million years ago), which caused the depth of the exsurgence. Above the spring there is a -high limestone cliff with innumerable breaks and faults. This acts as a reservoir, a karst aquifer, in which the water circulates along the discontinuities until it meets a barrier of limestone and clay. The spring, which feeds the River Sorgue, is the only exit point of a underground basin, which captures waters from Mont Ventoux, the Vaucluse Mountains, the Albion Plateau(fr) and the Lure Mountain(fr). The water of this exsurgence contains an average of of calcium carbonate, and has an annual flow of about , so the reservoir loses of limestone each year. This karstification phenomenon acting on the surface of the impluvium, removes an annual volume of per square kilometre, which disappears after being dissolved in the water. That figure becomes more meaningful when calculations show that, in 3.5 million years, the Vaucluse Mountains, the Albion Plateau, and the Lure Mountain, will have had their thickness reduced by . History In antiquity the site was a place of ritual offerings. During various dives, particularly in 1998, the members of the Fontaine-de-Vaucluse Speleological Society (SSFV), were intrigued by the presence of many