The Swiss canton of Valais, deep in the Alps in the southwest of the country, boasts a staggering 51 peaks that rise above 4,000 meters in altitude, among them the Dufour, the highest in Switzerland. It is also the place where the Rhône River is born, the most important of the great rivers of Central Europe that flows into the Mediterranean.

Before leaving Switzerland and entering France, the Rhône flows into Lake Geneva, a place that for many centuries was the main access point to the canton from the outside, until the construction of numerous railway tunnels beneath the great mountain chains, whose roads are almost permanently closed during winter.

Valais is rich in water, as it is home to no less than 56 percent of all Swiss glaciers, including the Aletsch, considered the largest in Europe.

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Aerial view of the Grande Dixence dam in the canton of Valais, Switzerland. Credit: Jérémy Toma / Wikimedia Commons

That’s why, as early as 1922, the company Energie Ouest Suisse saw the site’s potential for generating electricity, and five years later they had already secured the rights to exploit the upper basin of the Dixence River, in the val d’Hérémence.

There, they built an 87-meter-high dam that by 1935 was already powering a hydroelectric plant in Chandoline.

But the growing demand for energy meant that by the late 1940s, the need for expansion was being considered. Thus, in 1950, the company Grande Dixence was founded with the goal of building a new dam, much larger than the previous one.

grande dixence dam swiss alps
The dam seen from below, at 285 meters high, the highest in Europe. Credit: Simplon2010 / Wikimedia Commons

The project lasted 11 years and involved more than 3,000 workers, many of them Italian immigrants, who had to face extreme conditions with freezing winters, avalanches, and the difficulties of transporting materials to over 2,365 meters in altitude by truck and cable car.

Interestingly, among the laborers was a young Jean-Luc Godard, the famous filmmaker of the Nouvelle Vague, who shot his first documentary there precisely about the construction of the Grande Dixence dam, titled Opération Béton (Operation Concrete).

The construction of what is today the tallest gravity dam (a dam designed to hold back water by using only the weight of the material and its resistance against the foundation) in the world and the highest in Europe at 285 meters (roughly the height of the Eiffel Tower without its antenna) was completed in 1961 and officially inaugurated in 1965.

grande dixence dam swiss alps
View from the top of the dam. Credit: Huk2020 / Wikimedia Commons

The structure is 700 meters long at the top and reaches 200 meters thick at the base, gradually narrowing to 15 meters at the summit.

To secure the dam, a grout curtain was built around it, reaching a depth of 200 meters and extending 100 meters to each side of the valley.

It holds back the Lac des Dix, a reservoir about 4 kilometers long that contains 400 million cubic meters of water, making it the largest alpine lake above 2,000 meters in altitude, and supplying enough hydroelectric power to sustain 400,000 Swiss households.

grande dixence dam swiss alps
View of the old dam, while the Grande Dixence was being built in front of it. Credit: Werner Friedli / ETH Library / Wikimedia Commons

Power is produced by four hydroelectric power plants, three of them subway. One of the latter, Bieudron, has the highest waterfall in the world at 1800 meters, and is capable of varying its power from 0 to 1200 MW (equivalent to the power of a nuclear reactor) in just 3 minutes.

Beneath the waters of the Lac des Dix, fed by the Dixence River and by four pumping stations that capture meltwater from the surrounding glaciers through a labyrinthine system of 100 kilometers of tunnels, the old 1935 dam still remains. It can be seen when the reservoir level drops, creating a unique sight in the world of two parallel dams.

The colossal dimensions of the Grande Dixence cannot be fully appreciated in photographs—no image does justice to its true scale. It’s one of those places that must be experienced in person.

This article was first published on our Spanish Edition on May 20, 2025: La colosal Grande Dixence, la presa más alta de Europa que retiene el mayor lago alpino sobre los 2000 metros

SOURCES

Grande Dixence, Une véritable épopée technique et humaine

Dictionnaire Historique de la Suisse DHS, Grande Dixence

Denis Favre (CSIC), Presa Grande Dixence

Wikipedia, Lago des Dix

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