The Sierra de Gredos is a mountain range in central Spain that spans the provinces of Ávila, Salamanca, Cáceres, Madrid, and Toledo. It is part of the much larger Sistema Central of mountain ranges. Its highest point is Pico Almanzor, at 2,592 metres and it has been declared a natural park by the Autonomous Community of Castile and León. The Sierra de Gredos is one of the most extensive mountain ranges of the Central System; it comprises five river valleys: the Alto Tormes, the Alto Alberche, the Tiétar Oriental, the Tiétar Occidental y la Vera, and the Valle del Ambroz. The first known inhabitants were the Vettones, a pre-Roman Celtic people. The central part of the range encomprises the Sierra de Gredos Regional Park.