Built in the 1950s, the Mauvoisin dam is the second largest in the state of Valais (with 211.5 million cubic metres retaining volume) and the highest arched dam in Europe at 250m. In 1818, following the rupture of a natural ice dam, 18 million cubic metres of water destroyed everything in its path, killing 44 people. Since then the Mauvoisin dam has been used for energy production but also as protection against natural disasters. Visits to the dam on request for groups (minimum ten people) from Monday through Friday. The route around the Lac de Mauvoisin provides a fantastic if demanding excursion (seven hours).