The lake dam is a must-see in the area, discover it on the heights while hiking or come and visit it as part of our guided tours.

[Updated March 27, 2024]

Following a government decision and the reinforced vigipirate plan, guided tours of the Guerlédan hydroelectric dam are canceled until further notice.

A spotlight on Brittany

The Guerlédan dam was built at the beginning of the twentieth century. Its construction, decided just after the First World War, is above all the result of the meeting of two visionary men: Joseph Ratier, sub-prefect of Pontivy, and Auguste Leson, a young engineer with a degree in electricity. We are at the very beginning of the 1920s, a time when the State launched a major national electrification plan.

The works

After around ten years of studies and work, the dam was built in 1929 and the following year, it provided electricity to a large part of Brittany. At the time, there was talk of a concrete giant that would bring the “electricity fairy” into homes.

Yohann Hamonic

Its dimensions

The construction of the dam was a true technical feat. It measures 45 meters high, 210 meters long, which at the time made it one of the first and one of the highest dams in France. The project was titanic for the time. It was necessary to sink 110 m3 of concrete, a new material for the time.

Did you know?

The work might never have seen the light of day. Its construction encountered numerous technical and financial difficulties. If the project was completed, it is thanks to the determination of the actors and decision-makers of the time, and the context in which electrification constituted a national priority.

The construction of the dam gave birth to the Guerledan Lake which, for around ten kilometers, winds between Côtes d'Armor and Morbihan.


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