Azienda Energetica Metropolitana (AEM)'s 150-MW Pont Ventoux-Susa hydroelectric plant in Piemonte, Italy is designed to provide the area with an additional 457GWh/year. Most of the plant is built underground. The design and construction of the hydroelectric scheme was awarded to Pont Ventoux Scrl. Alpina was appointed engineering consultant for the design and underground works. The geology of the site is described. Tunnels were constructed by tunnel boring machines and by the drill and blast method. The design of the power cavern is described. Selection of the support system in the cavern, the cavern excavation, and use of the DEM numerical method to simulate the rockmass performance are discussed.