Lac de Paladru

Lake Paladru is a natural lake tucked into the Isère department, in the Auvergne-Rhône-Alpes region of southeastern France, at the foot of the Chartreuse massif. It sits roughly 40 kilometres northwest of Grenoble, near the village of Charavines, at an altitude of about 500 metres. Formed in a glacial basin, the lake stretches around 6 kilometres in length and just over 1 kilometre in width, covering nearly 400 hectares and ranking among the largest natural lakes in France. Beneath its calm surface, though, lies something far more unusual than scenery: the remains of a medieval settlement that archaeologists have been piecing together for decades.

What makes the water so distinctive?

Visitors are often struck by the lake's remarkable clarity and turquoise tint, visible even from a distance along the shoreline roads. That clarity, combined with summer water temperatures that can reach 25 degrees Celsius, makes Lake Paladru one of the more inviting spots for swimming in the region — warm enough to enjoy without the shock of typical alpine lake water.

Where can you swim?

Supervised beaches line the lake in four communities: Charavines, Le Pin, Montferrat and Paladru. Of these, only the beach at Charavines is free and open to everyone, while the others may charge an entry fee. The shoreline is set up for full-day visits, with grassy areas for relaxing and seasonal food stands nearby.

What can you do on the water?

The lake is a genuine hub for water sports. Rental outfits based around the shore — in Charavines, Le Pin, Paladru and Montferrat — offer paddleboards, kayaks, canoes, pedal boats, and equipment for sailing and rowing, catering to complete beginners and seasoned paddlers alike. Beyond the water, hiking and cycling routes wind through the surrounding hills and forest, offering views back down over the lake.

What lies beneath the surface?

The lake's most remarkable story is archaeological. In 1921, during an unusually low water level, researcher Hippolyte Müller spotted traces of ancient settlement on the lakebed — both a Neolithic site known as Les Baigneurs and a medieval one called Colletière. Systematic excavation did not begin until the 1970s, and it proved groundbreaking: this was where stratigraphic underwater excavation was first carried out in France, a technique that had not previously been attempted in this environment.

Colletière turned out to be a fortified 11th-century settlement covering roughly 1,300 square metres, built on a small peninsula that has since vanished beneath the water. Enclosed by a wooden palisade and reached by a timber walkway and drawbridge, it once housed knights, farmers and craftsmen. Because wood and other organic materials survive far better underwater than on dry land, the site preserved objects of daily life in exceptional detail, giving researchers an unusually vivid picture of how its inhabitants actually lived.

Where can you see what was found?

Finds recovered from the lakebed are now displayed at the Musée archéologique du lac de Paladru, a museum that opened in June 2022 directly on the lakeshore. Its exhibits walk visitors through the diving campaigns and the underwater archaeology techniques used to bring the settlement's story to the surface.

Frequently asked questions

Can you swim in Lake Paladru? Yes — supervised beaches operate in four lakeside villages, and summer water temperatures make swimming comfortable.

Is entry to the beaches free? Only the beach at Charavines is free; the others may charge admission.

What was discovered on the lakebed? A fortified 11th-century medieval settlement called Colletière, along with an older Neolithic site, Les Baigneurs.

Where can I learn more about the archaeological finds? At the lakeside archaeological museum, which opened in 2022 and displays objects recovered from the underwater excavations.