Aldeadávila Dam is a concrete arch-gravity dam on the Duero River (also known as the Douro River) in Spain, near the border with Portugal. The nearest town is Aldeadávila de la Ribera in the Province of Salamanca, about to the east. The nearest Portuguese town is Fornos in Bragança District, about to the southwest. The Portuguese side of the river around the dam site lies within the Arribes del Duero Natural Park. Overview In 1864, Portugal and Spain signed the "Treaty of Limits" (ratified in 1866), which established the present international boundaries of the two nations. A treaty on transboundary rivers, clarifying issues regarding the use of such rivers, was signed and affirmed in 1912. A treaty regulating the development of hydroelectric facilities on the Duero River was signed in 1927. The Aldeadávila Dam was built by Spain pursuant to these treaties, and was the final dam to be built by Spain on the section of river allotted to that country. The dam is high and its cost was estimated in 1962 at US$60,000,000 (about $443.5 million in 2010 inflated-adjusted dollars). It was one of a series of very high dams built in Europe in the two decades after World War II; these were designed with a downstream face inclined toward the upstream flow. This simplified the dam's design and construction (although it required more concrete to build), and more readily incorporated the spillways into the dam face. The dam's face is nearly vertical. Design work on the dam began in 1956, and construction completed in 1963. The structure was built by the Iberdrola Ingeniería y Construcción construction firm. Pedro Martínez Artola was the design engineer. The dam was built on high-quality granite rock. During construction, grouting was used to fill cracks in the rock which ran parallel to the dam's foundation, and on the Portuguese bank where two fractures in the rock occurred. The underground power station and tunnels were excavated using a mining procedure known as large-chamber stoping. The use of this technique for the Aldeadávila Dam is considered a textbook example. The turbine and generator hall, and the transformer hall were both cut from solid granite as well. The turbine and generator room is long, wide, and deep. The total volume of excavated material for all halls, rooms, and abutments was . The structure has eight overflow gates which channel water into four spillways. The spillways incorporate