Fuerteventura, with a surface of 1,660 km2 (640 sq mi), is the second-most extensive island of the archipelago. It has been declared a Biosphere reserve by Unesco. It has a population of 113,275. Being also the most ancient of the islands, it is the one that is more eroded: its highest point is the Peak of the Bramble, at a height of 807 metres (2,648 feet). Its capital is Puerto del Rosario.