The site ranges in altitude from 1,645 m in the bed of the Oued Arheddou to 3,102 m at the summit of Jbel Tanrhourt. At its western end it includes the twin lakes of Isli and Tislit, near Imilchil. The northern slopes enjoy an annual precipitation of 400–600 mm, and are consequently well-wooded, while the southern slopes are drier, receiving only 200–300 mm, and are more open.