The Ordesa Valley is a glacial valley in Aragon, in the Spanish Pyrenees which forms part of the Ordesa y Monte Perdido National Park. It was first discovered in 1820, but not mapped in detail until approximately the 1920s. The valley is about 11 kilometres long. The valley's east–west orientation, unusual in the Pyrenees, opens it to influence from the Atlantic Ocean and gives it a moderate climate.