Lagoa do Caiado

Lagoa do Caiado is the largest lake on Pico Island, Azores. The high-altitude lake is located on the Achada Plateau, an extensive volcanic mountain range covering most of the central area of the island. The waters are clear and are used for public supply since 1993.Sitting at around 822 m in altitude, in a cinder cone dominated landscape, the area around the lake is densely vegetated due to the extreme humidity it gets. Unlike the rest of the Azores, which have been subject to introduction of exotic species, most of the plant-life around the lake is endemic to the archipelago.

Source: Wikipedia