The Côa Valley is not a gallery with a roof. Its archaeological record follows rock surfaces in a rugged landscape where the Côa meets the Douro in northeastern Portugal. Across the border in Spain, the engravings at Siega Verde follow the Águeda River. UNESCO treats the two areas as one serial World Heritage property because their open-air images illuminate related chapters of Upper Paleolithic life on the Iberian Peninsula.
The story of the Portuguese discovery is inseparable from a modern controversy. The first engraved panel identified at Canada do Inferno was found in late 1991; the art became public in 1994, while plans for a dam on the Côa were advancing. The archaeological significance prompted a national debate over whether the valley should be flooded for a hydroelectric project or protected. In 1996 the Portuguese government abandoned the dam plan, allowing the rock-art landscape to remain in place.
