The trade in Pu’er tea was not a one-way journey, and few if any caravans journeyed the entire distance. Instead, at staging posts like Lijiang and Gyalthang (later to become Shangri-La), the tea was off-loaded and replaced with goods from the north bound for southern Yunnan. One of the most valuable was salt, which has a special importance in mountains like the Himalayas because of the traditionally high incidence of goitre, caused by lack of iodine in the diet. 140 kilometres north of LUX Benzilan are the unique Yanjing Salt Pans (Yanjing means Salt Well in Chinese). Wells on either side of the torrential Mekong River tap into saline aquifers, which villagers have drawn for more than a thousand years. The only problem is that there is no flat land for evaporation, only the rocky gorge. The solution was to build 2,800 salt pans of timber and mud, ranged over the steep slopes. Each morning, the villagers take the salt water up the slopes and empty their buckets onto the shallow pans, each about 20 square metres in area. The strong sunshine and winds sweeping up the gorge do their job over the course of the day, and by afternoon the dried salt is ready to be collected—white salt on the right bank, red salt because of iron oxide on the left bank. Ironically, given the high regard that Himalayan red salt is held in the West and its consequently high prices, this local variety, called Peach Salt, sells more cheaply than the white.