Some residents barely have a name.
That's where many homeless go on cold nights to escape the bitter wind and sleep for a few hours on the warm ventilation grates. Some stay just for a night or two, some for an entire winter, a few even longer. On a Chicago winter night, with the windchill far below zero, the cover of the city above and heat of the warm grates below can be literally the difference between life and death. I know it's there. I've slept down there myself.