The Lac de Serre-Ponçon in the French Alps gathers the waters of the Durance and the Ubaye rivers behind a 123-m high dam built 1955-61. The water storage prevents floods, supports irrigation and enables the operation downstream of 16 hydroelectric plants. The dam – the Barrage de Serre-Ponçon – was constructed by moving 3 million cubic metres of earth. Several settlements were flooded. The reservoir has a surface area of 28 square kilometres. The power plants at the dam is the largest in the system and generates 380 megawatts for EDF Odysselec. The visitor centre at the foot of the dam interprets the construction, hydroelectricity and the uses of water through interactive play, archive photographs and films. Visitors see the generating hall of the underground power station and can follow a trail around the landscape. Visits to the power station itself must be booked in advance.