Upper Mustang of Nepal is on an ancient trade route between Nepal and Tibet exploiting the lowest pass Kora La through the Himalaya west of Sikkim. This route remained in use until China's annexation of Tibet in 1950. China eventually decided to revitalize trade and in 2001 completed a road from the international border to Lo Manthang. Across the TAR border is Zhongba County of Shigatse Prefecture. China National Highway 219 follows the valley of the Yarlung Tsangpo River some north of the border. Till today Manang and Humde are accessible only on feet or on horseback.