It comprises two main canyons—Canyon de Chelly to the south and Canyon del Nuerto to the north—which join at the monument's western end. Numerous side canyons lead from the main ones. Lining these canyons are several hundred pre-Columbian cliff dwellings (cliff dwelling), built at the base of red sandstone cliffs or in caves on the steep canyon walls. They cover a longer period than any other ruins in the Southwest, dating between AD 350 and 1300. Relics of the Basket Maker culture have been found under those of the later Cliff Dweller and Pueblo (Pueblo Indians) cultures. Modern Navajo homes and farms occupy the canyon bottoms.