Monastery beneath Lake Vouglans

The Chartreuse de Vaucluse, a 12th-century monastery, lies submerged under Lake Vouglans in the Jura region. It was submerged when the dam was filled between 1968 and 1969, resting between 50 and 90 meters below the lake’s surface.

Diving expedition explores submerged ruins

In June 2023, a diving expedition explored the monastery’s halls, descending to 80 meters below the surface. The team, led by underwater photographer André Reumaux, discovered about fifty rooms spread across three levels, including an intact cooking piano in what was once the kitchen.

The dam’s massive scale

The dam that created Lake Vouglans is 103 meters high and 427 meters wide at the crest. It contains about 545,000 cubic meters of concrete and holds 600 million cubic meters of water, equivalent to 240,000 Olympic swimming pools.

Lake Vouglans’ vast expanse

Lake Vouglans stretches over 35 kilometers and covers 1,600 hectares, an area larger than 2,000 football fields. It is the third-largest artificial lake in France and was formed during the dam’s filling in the late 1960s.

Monastery’s history and destruction

The Chartreuse de Vaucluse was founded in 1139 by Carthusian monks in a secluded valley. It was partially destroyed during Louis XI’s campaigns, later rebuilt in the 18th century, and eventually became a farm. It was listed as a historical monument in 1927 before being submerged in 1969.

Some parts of the monastery remain above water

Before the lake was filled, the monastery’s 18th-century portal and entrance pavilions were removed and rebuilt on solid ground upstream of the village of Onoz. Reconstructed remains are also visible near the hamlet of Chavia.

Challenges of the underwater dive

The 2023 dive took place in water at about 4 °C, requiring specialized equipment such as rebreathers, which allow divers more autonomy without releasing bubbles. The team made three dives of 20 minutes each, a short duration given the extensive preparation needed.

Safety concerns and accessibility

A 46-year-old diver died on April 6, 2026, due to a faint at the site. Diving in the area is restricted to experienced divers through local clubs or professionals. No official authorization has been confirmed for the 2023 expedition, and the site is not freely accessible.

Lake Vouglans as a recreational area

Above the submerged ruins, Lake Vouglans is a popular recreational spot. Visitors engage in activities like fishing, motor boating, sailing, and rowing. Hikers can follow the shoreline to a cross that overlooks the lake, with buoys marking the location of the monastery’s remains more than 45 meters below the surface.