Fontaine de Vaucluse

The source of the Sorgue and the largest karst spring in metropolitan France according to its commune. Its flooded shaft has been explored by divers and robots to a sandy floor at 315 m; the municipality banned diving in 1974, and later work has been research-led.

The Fontaine de Vaucluse lies at the foot of a cliff more than 240 m high and drains rain and snowmelt from a catchment of about 1,240 km², including the southern slopes of Mont Ventoux, the Monts de Vaucluse and the Montagne de Lure. In spring and autumn floods the pool overflows spectacularly; at other times the Sorgue is fed by lower secondary springs.

The flooded shaft below the pool has drawn divers since a Marseille helmet diver reached 23 m in 1878. Cousteau and Dumas made the first self-contained dives here in 1946, reaching 46 m. In 1981 Claude Touloumdjian reached 153 m with COMEX support; Jochen Hasenmayer, who had dived to 140 m without authorisation a few days earlier, returned alone in 1983 and reached 205 m. On 2 August 1985 the remotely operated Modexa landed on a sandy floor at 315 m, still the known terminus.

The local caving club, the Société spéléologique de Fontaine de Vaucluse (SSFV), has led most later work, including its own Spélénaute robot (1989-1996) and, from 2001, archaeological prospection that recovered more than 1,600 Roman-era coins and objects under the direction of the State's underwater archaeology service.

The commune states that a 1974 survey dive with an undisclosed commercial aim led the municipality to prohibit all diving. Visitors are asked not to cross the safety barriers at the pool because rocks fall from the cliff with potentially fatal force.

The commune gives an annual discharge of 630 to 700 million cubic metres, flood flows of around 90 m³/s and a near-constant water temperature of 12.5 to 13 °C. Showcaves notes that for much of the year the main shaft does not overflow and water emerges from lower outlets in the riverbed. In August 2022, when flow at the station fell to the regulatory threshold of 4 m³/s for two days, navigation and underwater activities were banned on the Sorgues under a prefectural order of 28 May 2019.

A classic site in the history of diving and cave exploration, from early helmet dives to Cousteau's first autonomous dives and record robot descents, and an archaeological site whose submerged Roman coins led to protection measures by the Ministry of Culture.

Flow varies greatly with season: floods in spring and autumn, low summer flow when the pool may sit below its rim. Rockfall from the cliff is a hazard at the pool.

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One entrance, the spring pool at the foot of the cliff, reached by a public footpath from the village.