The Undercity? Um... it's- well, it was built under the mountains at the top of Sidereal. And the Bloo Stream would run through it and caused lots of radiation. It was dark down there, even though they had artificial lights to simulate daylight and stuff... and if buildings collapsed, they just built right on top of them.

It was horrible. That's why I left to get a job somewhere nicer as soon as I was old enough.