Les Trois Pierres

Les Trois Pierres is a lighthouse standing on a rocky spur at the northeastern tip of Lédénez de Molène, within the Molène archipelago in the Iroise Sea, in the Finistère department of Brittany, France. It's one of the landmarks visible from Île-Molène itself, a small island where daily life has long followed the rhythm of the sea and the work of its lighthouse keepers.

Where is the lighthouse and what does it look like?

Les Trois Pierres is a white column-shaped tower roughly 15 metres tall, built on a rocky base right at the entrance to the channel known as the passe de Molène. Its slim, plain silhouette and white paint make it easy to spot from a distance, even in the fog that frequently rolls over these waters. The structure was never meant to be decorative — its job is to guide sailors safely between the many rocks and shoals that surround the archipelago.

What role does the lighthouse play for navigation?

Les Trois Pierres marks the entrance to the passe de Molène, a narrow and demanding passage between the islands of the archipelago. It doesn't work alone: its signal is backed up by the smaller markers of Basse Réal and Roche Goulin, which together form a system that leads ships safely through this stretch of the Iroise Sea. The light itself is isophase with a 4-second period, meaning equal spells of light and darkness — a rhythm sailors can recognise even in poor visibility.

Why does the light change colour?

One of the defining features of Les Trois Pierres is its coloured sectors, which shift between green, white and red depending on the bearing from which the light is seen. The green sector runs from 070° to 147°, white from 147° to 185°, red from 185° to 191°, green again from 191° to 197°, white from 197° to 213°, and red from 213° back to 070°. This division lets sailors instantly judge which side of the safe course they're on: white marks clear water, while the coloured sectors warn of nearby rocks. The white light carries a range of 9 nautical miles, while the green and red sectors reach 6 nautical miles.

What is the Molène archipelago, and why does it have so many lighthouses?

The Molène archipelago is a chain of 19 islands and islets stretching some 16 kilometres between Le Conquet on the mainland and the island of Ouessant. This part of the Iroise Sea holds the largest concentration of lighthouses anywhere in Europe — strong currents, hidden rocks and sudden weather changes have long demanded a dense network of markers to keep shipping safe. Les Trois Pierres is one link in that chain, and it's also one of the stops on Brittany's Route des Phares, the touring route that connects the region's best-known lighthouses.

How can visitors see the lighthouse from Île-Molène?

The lighthouse is visible from the shore of Île-Molène and serves as a natural point of reference for walks around the island or boat trips through the archipelago. Because the rocky ground around it floods with the tide, reaching the tower itself calls for caution and is best done on an organised boat excursion — the kind that also takes visitors past the archipelago's other lighthouses, such as Kéréon and La Jument.

Frequently asked questions

Where exactly is the Les Trois Pierres lighthouse? On a rocky spur at the northeastern tip of Lédénez de Molène, within the Molène archipelago, in the Finistère department of Brittany.

How tall is the lighthouse? The tower stands about 15 metres tall on a rocky base.

What is Les Trois Pierres used for? It marks the entrance to the passe de Molène and warns sailors away from nearby rocks through its coloured light sectors and a 4-second isophase signal.

Can visitors walk up to the lighthouse while touring Île-Molène? It's best viewed from a safe distance, either from the island's shoreline or during a boat trip — the ground around the tower is rocky and gets covered by the tide.