Water is the main feature of this national park which is located in the heart of the Lleida Pyrenees and which offers the finest example of natural mountain scenery.

The park is notable for its beautiful landscapes, for the harmonious combination of lush forests and green meadows and for its rich flora and fauna. The age-old forests of fir and black pine are home to the rare quebrantahuesos ("bone breaker"), the bearded vulture. The area is notable, too, for the waterfalls and immaculate snow, but above all, for the nearly 200 mountain lakes and ponds, the estanys for which it is named.

It lies between the rivers Noguera Pallaresa and Noguera Ribagorzana and is made up of two valleys: the Sant Nicolau, accessed from the village of Boi, and la Escrita with its centre in Espot. At 3,033 metres, Comaloforno is the highest peak, but the best known symbol of the park is the Els Encantats massif, two huge forms that rise to 2,747 metres opposite the Sant Maurici lake.

The aigüestortes or "twisted waters" are to be found in the valley of Sant Nicolau. They cover a large area and are so emblematic that they, too, form part of the park's name. Around and about are a number of small villages with well-preserved Romanesque churches which have been declared a World Heritage Site by Unesco.