Reservoirs of Duero (Iberian Pen) #1 Aldeadávila3D Model
Aldeadávila Dam is a concrete arch-gravity dam on the Douro River (also known as the Duero River) on the border between Spain and Portugal. The dam is 140 metres high. The canyon through which the Douro River flows is exceptionally deep and narrow, resulting in a reservoir that has a relatively small surface area for its immense size (Wikipedia)
Photogrammetric survey: PNOA © Instituto Geográfico Nacional-Junta de Castilla y León.
Photo by Raiden32 (Wikimedia)