Ba Sing Se

The largest city in the world, Ba Sing Se is practically a kingdom unto itself; the Earth King's palace a small city. The metropolis is bounded by the great inner Wall, and beyond it stretches an Agricultural Zone large enough to feed the entire city, terminating with the Outer Wall. Within, further walls divide the city into the Upper, Middle, and Lower Rings, emblematic of its stratified class system. Proof of residence in the Middle or Upper Ring, or other permission, is required to get into the latter.