This hilly region is traversed many mountain streams, called gaves: among these include the Gave de Pau, the Gave de Bious the Gave d'Ossau or the Gaves réunis, on the border of Landes and Pyrénées-Atlantiques. Ossau Valley, one of the three valleys of Béarn, extends from the suburbs of Pau to Col du Pourtalet to the Spanish border. Glacial lakes, its fauna and flora exceptional explain its integration into the Pyrénées National Park.