The Gargantuan Outer wall of Ba Sing Se is arguably one of the most impressive defensive positions created in the entire world. Spanning wider than many men laying down head-to-toe, and much higher than any kind of average wall, the Outer Wall is the first area of entrance to Ba Sing Se. The only people able to open the wall are earthbenders, seeing as there are no gates or anything of the sort. Between the first outer wall and the second wall are mainly fields for food production. The wall itself has only been breached once in its long history.
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Ba Sing Se's outer wall is the city's thickest layer of protection. The Wall is huge. Easily a hundred meters tall and perhaps thirty meters thick, it is the largest man-made structure in the World of Avatar. The Wall encircles all of Ba Sing Se, along with the vast agrarian zone and a medium-sized lake. It is considered indestructible and is commonly drawn on maps as a terrain feature. In fact, it has only been breached twice: once by General Iroh, once by the drill. Since then, the Fire Nation has mounted a continuous assault on the city to little avail. The Dai Li mandates that soldiers and sentries be placed on the wall at all times, with many of them even living in built-in homes inside the wall. After the Coup of Ba Sing Se, Dai Li agents tore a hole in the wall to allow Fire Nation soldiers through. The tear had not been repaired by the time the Order of the White Lotus attacked, and apparently the wall was not being monitored at the time.
