The Aran Valley is a small valley (620.47 km²) in the Pyrenees mountains and a comarca (county) in the northwestern part of Catalonia, Spain. Most of the valley constitutes the only part of Catalonia on the north face of the Pyrenees, hence the only part of Catalonia whose waters drain into the Atlantic Ocean. The region is characterized by an Atlantic climate, due to its peculiar orientation, which is different from other valleys in the area.
The Aran Valley borders France on the north, Aragón to the west and the Catalan comarques of Alta Ribagorça to the south and Pallars Sobirà to the east. The capital of the comarca is Vielha, with 3,692 inhabitants (1996). The entire population of the valley is about 7,130 (1996). The Garonne river passes through the Aran Valley after rising on the slopes of nearby Pic Aneto and passing underground at the Trou de Toro. It then reappears in the Val dera Artiga as a resurgence and flows into the Aran Valley which is one of the highest valleys of the Pyrenees. The Noguera Pallaresa, with its head only a hundred meters from that of the Garona, flows the other way, toward the Mediterranean.
The Aran Valley used to be without direct communication with the south side of the mountains during winter, until the construction of the Vielha tunnel, opened in 1948. Spanish Republican guerrillas controlled the area from the end of World War II until the opening of the tunnel.
