This very popular route heads 8km (with 500m ascent) along the Valle de Ordesa from Pradera de Ordesa, between soaring cliffs and passing numerous waterfalls, to the Circo de Soaso, a rock amphitheatre decorated by the Cola de Caballo (Horsetail) waterfall, where Monte Perdido towers far above. Return the way you came. The 16km round trip takes about 5½ hours plus stops.

If you don't fancy the whole route, it's still worth walking as far as some of the waterfalls on the Río Arazas, eg the Cascada del Estrecho (3km, one hour from Pradera) or the Gradas de Soaso (6km, 2¼ hours).