Known as Jehol or "Rehe", Chengde, is an 18th-century imperial resort area, about 250 km northeast of Beijing. Surrounded by mountains, Chengde lies on the area between the Mongolia Plateau and the Huabei Plain. The early Qing emperor Kangxi discovered it in the late 17th century, who found the cool summer climate and natural scenery appealing as a summer retreat. Kangxi and his successors built some 72 palaces there by the end of the 18th century, along with replicas of the Potala Palace of the Tibetan Buddhist lamas. Today Chengde is one of the 24 historical cities protected by the State Council and is an UNESCO Heritage site.