Trou du Diable

Trou du Diable is a sea cave and cave entrance near Saint-Hilaire-de-Riez on the French Atlantic coast. A natural portal opens about 5 meters above the water level and leads into a cavity roughly 20 meters long, carved through ancient Silurian micaschist rock.

This cavity formed over millions of years as waves gradually carved through the ancient rock. In 2010 the local authorities installed protective barriers to prevent access to a natural stone bridge that once allowed people to walk directly above the cave opening.

Local stories speak of the Fradets, mythical beings said to inhabit the sea caves scattered along the Corniche de Rié coastline. These tales remain part of how visitors and residents think about the rocky shores here.

Access is via the Chemin Les Duprat walking path, with viewing areas protected by safety railings. Visit during calm weather to safely enjoy the cave and observe the surrounding coastline.

The name comes from a striking phenomenon: water inside the cave appears to boil like a cauldron when waves surge through the opening. This dramatic effect happens because Atlantic waves regularly force their way into the cavity with considerable force.

Location: Saint-Hilaire-de-Riez

Elevation above the sea: 5 m

Address: Corniche Vendéenne, 85270, France

GPS coordinates: 46.69732,-1.97280

Latest update: December 6, 2025 17:41