In the first years of the Han, Liu Bang fixed his capital at Chang'an, inside the passes.
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usage
关 is a pass. In modern use it is 山海关, where the Great Wall meets the sea, so 关内 is the land inside it and 关外 or 关东 the Northeast beyond. In Qin and Han writing the pass is 函谷关, and 关内 means the 关中 plain.
