The Pyrenees National Park encompasses a mountainous strip of land along the border; 1-15km wide and 100km long, it lies between the Aspe Valley to the west and the Aure Valley to the east. It takes in six valleys, four of which are in the Hautes-Pyrénées: Arrens, Cauterets, Gavarnie and Aure. Stopping in at one of the Maisons du Parc visitor centres is a good prelude to an excursion that promises magnificent waterfalls, lakes with emerald green waters, bubbling sinkholes and majestic peaks.