Héngduànshān

The southern Hengduan ranges enclose the uplands of Yanyuan in a maze of ridges, basins and river valleys. West of the Yalong, the mountains continue towards the Sichuan-Yunnan frontier, where Lake Lugu lies among high slopes. The broken terrain divides neighbouring basins from one another, while valleys through the mountains have long offered passages between the highlands and the warmer country along the Jinsha River.