Deep in the mountains of western Sichuan I'm hacking through a bamboo jungle, trying to find a legendary trail. Just 60 years ago, when much of Asia still moved by foot or hoof, the Tea Horse Road was a thoroughfare of commerce, the main link between China and Tibet. But my search could be in vain. A few days earlier I met a man who used to carry backbreaking loads of tea along the path; he warned me that time, weather, and invasive plants may have wiped out the Tea Horse Road.
Then, with one wide sweep of my ax, the bamboo falls. Before me is a four-foot-wide cobblestone trail curving up through the forest, slick with green moss, almost overgrown. Some of the stones are pitted with water-filled divots, left by the metal-spiked crutches used by hundreds of thousands of porters who trod this trail for a millennium.