Setting
The UnderCity could is city of its own, completely different from its above ground counter part; some people even choose to live there. Between the drugs, the danger, the hookers, and the slower pace; this is considered a vacation spot to some. Locals affectionately call this place Old New York.
Most of the buildings resemble those of the 21st century. Technology is just as advanced as top side, but rarely as most can't afford it. It is common to see some out of date things. Streets don't exist, there are just dirt roads littered with trash. There is a stench all around, nothing bad, but an air completely different from above. Sunlight rarely reaches these depths, which makes most of the people born there paler than normal. They are also a bit sun shy and more tolerate to cold temperatures.
The UnderCity is basically a built over Manhattan. Not being able to keep up with times, they were left behind. Ignored and forgotten, they forever remain in the shadows of the new and better city.