The "Green River" was a route pioneered by explorers of the past, a path that led through a series of lush oases at regular intervals. There were sixteen such oases along this route. In the desert, an oasis was the very Source of life; only by reaching them could one hope to cross the Great Desert.
Along the way, Zheng Xiu noticed that roughly every few dozen miles, there were small hills formed from piles of heavy stones. They didn't look natural; they seemed man-made. When Zheng Xiu casually asked about them, Xie Luohe said with a smile:
"Those are the 'Hou Mountains' on the Green River."
"So they are 'hou' after all."
The so-called "hou" are typically mounds of stone or earth found on official roads and side paths, used to mark distance. By counting the number of "hou" one passed, you could estimate how many miles you had traveled. But along the Green River, each "Hou Mountain" was a full ten feet tall. Barring a sandstorm, ordinary winds could hardly topple them.
