Lake Guerlédan is an artificial lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in the centre of Brittany

Brittany

Brittany is a cultural and administrative region in the north-west of France. Previously a kingdom and then a duchy, Brittany was united to the Kingdom of France in 1532 as a province. Brittany has also been referred to as Less, Lesser or Little Britain...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. It extends across the borders of the departments of Morbihan

Morbihan

Morbihan is a department in Brittany, situated in the northwest of France. It is named after the Morbihan , the enclosed sea that is the principal feature of the coastline.-History:...

 and Côtes-d'Armor

Côtes-d'Armor

Côtes-d'Armor is a department in the north of Brittany, in northwestern France.-History:Côtes-du-Nord was one of the original 83 departments created during the French Revolution on 4 March 1790. It was created from part of the former province of Brittany. Its name was changed in 1990 to...

, within the communes of Saint-Aignan, Morbihan

Saint-Aignan, Morbihan

Saint-Aignan is a commune in the Morbihan department of Brittany in north-western France.-Demographics:Inhabitants of Saint-Aignan are called in French Saintaignanais.-References:* * -External links:* * *...

 and Mûr-de-Bretagne

Mûr-de-Bretagne

Mûr-de-Bretagne is a commune in the Côtes-d'Armor department in Brittany in northwestern France.-External links:*...

. At an elevation of 121 m, its surface area is 4 km². Lake Guerlédan is the largest artificial lake in Brittany.

This Lake was created to power the dam of Guerlédan. Construction took seven years from 1923 to 1930, and encounted many geological, technical and financial difficulties. The creation of the lake and especially that of the dam cut the through the Nantes-Brest canal which from this location, followed the course of the river Blavet

Blavet

The Blavet river flows from central Brittany and enters the Atlantic Ocean on the south coast near Lorient. The river is canalized for most of its length and is navigable for smaller craft. It is part of Brittany's canal system and became more important when the western half of that system got cut...

. Seventeen of the old locks on the canal were submerged in the Lake. Lake Guerlédan is now a tourist attraction, offering various watersports, walks and panoramic views.

During World War II, the Breton nationalist architect James Bouillé

James Bouillé

James Bouillé was a French architect based in Brittany.-Biography:Bouillé was born in Guingamp He studied at the École des Beaux-Arts in Paris, until he was mobilized after the outbreak of the First World War in 1914...

advocated a radical plan to build a new Breton capital city on the shores of Lake Guerlédan, to be called "Brittia". Bouillé believed this could be a "Celtic Brasilia".

Beginning in 1951, the Lake was regularly drained every ten years, revealing a hidden landscape of submerged locks and buildings. Modern technology has rendered this draining unnecessary.