The Breil-sur-Roya hydroelectric generating unit was started in 1926 and commissioned around 1929, while the French and Italian Roya was in the process of electrification under the impetus of private companies.
A widening of the Roya river at the village level, followed by a rocky strangulation, was used to create a reservoir lake. In order to benefit from a maximum height of fall, the plant was established just north of the old Italian border marked by the Riou valley at Piène-Basse hamlet.
The water supply tunnel to the power plant is mostly underground, and has a very small difference in height to optimize the final waterfall in a double penstock. South of the village, an aqueduct crosses the Roya in the form of a tube carried by triangulated legs in reinforced concrete.
The Piène-Basse power plant, at an altitude of 230 m, impels the water captured at the gate of the village lake at an altitude of 280 m.
The building, built in 1926, presents the characteristics of modernist industrial architecture. Its halls are lit by large bay windows on the river side. A double reinforced riveted metal line runs along the slope from the exit of the adduction tunnel to the turbine room, crossing the Roya river.