"The Tea and Horse Road of Southwest China is less well known than the famous Silk Road. Its route crosses some very high and dangerous terrain. It begins from Sichuan and Yunnan provinces in Southwest China, runs along the eastern foothills of the Hengduan Mountains, a center of tea production in China, then crosses the Hengduan mountain range and deep canyons of several major rivers, the Yalong, the Jinsha (the upper reaches of Yangtze), the Lancang (Mekong), and the Nu (Salween), thus spanning the two highest plateaus of China (Qinghai-Tibet and Yunnan-Guizhou) before finally reaching India south of the Himalayas.
The name of the road indicates its importance in the trade of tea and horses, but other products passed along it as well. Horse caravans carried tea, sugar and salt from Sichuan and Yunnan to Tibet and brought back colorful local mountain goods. The Chinese over the ages often bought warhorses from Tibetan and other ethnic groups of Southwest China, and these too came over this road. The road also served as a significant corridor for migration as well as a channel for cultural communication among the ethnic groups in western China; beyond this, it was a bridge for international cultural and economic exchange between China and India. Although silk was not included in the trade goods carried over it, at times it has been termed the “Southern Silk Road of China,” due to its importance in both economic and cultural aspects of Chinese history.
... According to the surveys, the tea and horse route from Sichuan to Lhasa is some 2350 kilometers long, with fifty-six traveling stages. One has fifty-one river crossings, fifteen rope bridges and ten iron bridges and traverses seventy-eight mountains over 3000 meters high. All of this makes the route one of the most difficult in the world. "