Ordesa y Monte Perdido holds the honour of being the second oldest national park in Spain, as well as earning the titles of Biosphere Reserve and World Heritage Site granted by Unesco. The Unesco titles are shared with the glaciers on the French slopes. Its 15,000 acres include one of the most unique ecosystems in the Pyrenees, formed by glacial erosion of the Arazas River valley.
In the park you will find peaks rising to over 3,000 metres, notable among which is Monte Perdido - the "lost mountain" itself. There are traces of glaciers, dense beech forests and a unique fauna, in addition to the highest limestone massif in Europe, where the action of water over millions years has carved out the monumental landscape of the Ordesa, Añisclo, and Escuain and Pineta valleys. Among them, Ordesa is the most famous, offering, as it does, a treasurehouse of waterfalls which tumble between its cliffs and gorges.
The most spectacular and most easily accessed of the waterfalls are el Estrecho and la Cueva. Higher up are the Gradas de Soaso, a flight of natural step-like projections formed by erosion by the Arazas. The farthest fall is the Cola de Caballo, where the water thunders against the rock wall that closes the head of the valley.