Setting
Ba Sing Se is the safest place for refugees displaced by the Hundred Year War because of the Fire Nation's failure to penetrate its walls.
Ba Sing Se is arguably one of the oldest settlements in the world. A five-thousand year old map to the city was found in Wan Shi Tong's spirit library, which suggests the city is at least that old. Early in its history, Ba Sing Se was a small subterranean city carved out of rocks by Earthbenders. As the benders excavated further, they came across beautiful illuminated crystals and began to mine them. The crystals currently serve as a common light source for Earth Kingdom inhabitants. Eventually, as the metropolis' expansion reached the surface, the catacombs were abandoned. The city continued to grow and eventually became the capital of the newly-unified Earth Kingdom. Although Ba Sing Se is the largest city in the world, no figures have been given for its population.
Ba Sing Se has been hailed as the greatest fortress in any of the four nations, having remained unconquered for centuries prior to the Hundred Year War. During Chin the Conqueror's largely successful campaign to unify the Earth Kingdom under his control, Ba Sing Se was the only territory to remain unconquered besides the peninsula where Avatar Kyoshi lived. Apparently, Chin would rather face the Avatar herself than try his luck at the Great Wall of Ba Sing Se.
After Chin's death, a peasant uprising erupted against the corrupt and inefficient government of the 46th Earth King. The peasants felt that the Earth King's role was outdated and that he did not represent their interests. Avatar Kyoshi managed to quell the revolt by forcing the King to accept the peasants' demands in exchange for creating the Dai Li to protect the government's interests.
The Dai Li are an elite organization of Earthbenders and the secret police of Ba Sing Se who worked to capture, interrogate, and imprison political dissidents. They were created by Avatar Kyoshi hundreds of years ago, with the aim of "protecting the cultural heritage of Ba Sing Se".
Law and order are maintained under the strictest of police forces to ensure that society does not break down into chaos. The people of Ba Sing Se have a variety of recreational activities available to them including spas, poetry houses, shops, restaurants, and the Ba Sing Se Zoo. Tea-drinking is one of the most common ways citizens relax after work, while strolls around the parks and shops of the Middle Ring are also enjoyed. Earthbenders are highly valued, and operate many civic projects, from the monorail system to the city's gates. A higher education can be gathered at the Ba Sing Se University.
The architecture of Ba Sing Se is slightly different from many other towns. The majority of the buildings are made of stone, with wood supports and plaster covering the outside. The color of roofing tiles on buildings indicate their prestige and vary by ring - Lower Ring buildings have black or dark green tiles, Middle Ring buildings have vibrant green, and the Upper Ring nobility uses yellow tiles as a sign of class. Earth Kingdom symbols are often placed on gates, government buildings, and military sites. Roads in the Middle and Upper rings are made of flagstones, while the Lower Ring has muddy dirt paths for most of its streets and alleys. The citizens of Ba Sing Se sport considerably more color variation in their clothing than citizens from other locations—blues, turquoises, browns, and golds can all be seen among the aristocracy, while the lower class usually wears browns, greens, and off-whites, although other colors can be seen.
The city is divided into various levels based on social class, with the poor and refugees living in ghettos walled off from the rest of the city. Society is heavily controlled, and the war is not allowed to be mentioned inside the walls. This is meant to maintain order and the cultural heritage of the city, making it the only remaining "Utopian" society in the world. The people of the city consider it impenetrable, and thus they often delude themselves into pretending all is fine in the rest of the Kingdom. Those who attempt to disrupt this fantasy are promptly brainwashed by the Dai Li into believing that the war does not exist.