Yu Men Guan & Yang Guan - By 111BC, Emperor Wu ordered the establishment of 4 counties along the Corridor. They were, front east to west, WuWei, ZhangYe, JiuQuan, DunHuang. To the west of DunHuang, a west bound passage to XiYu would split in to 2, one took a northern route and the other would take a southern course. Not too far from the county of DunHuang, 2 military passes were built to guard these 2 passages. They were the YuMeng Guan frontier pass up north and the Yang Guan frontier pass down south. From there on till the end of 10th century AD, passengers who traversed along these section of the Silk Road all had to go through either one of these 2 passes.

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The 4 pictures here showed: #1 the ruins of Xiao Fang Pan Cheng which was an office quarter of the commanding officer of Yu Meng Guan and a military storage; #2 the ruins of Da Fang Pan Cheng which was a forward military warehouse of Han armies used during a series of wars in XiYu around 103BC; #3 the remains of what used to be an associate beacon tower of the YangGuan; #4 views looking down from the beacon tower highland.