The upper Bionaz valley’s landscape changed between 1961 and 1965 due to the construction of the enormous Place Moulin dam. The dam create Lake Prarayer, an artificial basin nestled between the mountains. In the background you can see le Petites and les Grandes Murailles with their impressive glaciers.

This is the largest water basin in the region and one of the largest dams in Europe. Just a quick look at the structure’s statistics gives an idea of its phenomenal aspect:

• the dam is 155 metres high and 678 metres long
• maximum dam thickness at the base is 47 metres thinning to 6 metres thick at the top
• 1,510,000 cubic metres of cement were used to build the dam
• the maximum level reached by water is 1,969 m a.s.l.
• 105 million cubic metre is the dam capacity.

The dam exterior is always open to the public, but upon reservation it is possible to enjoy a guided tour inside in the period from May to September. The dam can be inspected on several levels that lower even under the lake waters and are connected by stairs and an elevator. Numerous machines and equipment tied to dam operations and safety controls are to be found inside.