Oh yeah, forgot to mention that this is location (along with a lot of the underground stuff) is inspired by the Buffalo Bayou Park Cistern, a fascinating little bit of Houston history.  Houston itself also has an actual underground tunnel system for pedestrians that's much nicer than Metacarpolis', kind of like a Japanese depachika, but of course it is constantly getting flooded.  I haven't been in them myself because I didn't learn about these places until I was already well into college and moving around, and they're only really open during the business day so it's me versus everyone else commuting in and out of Houston.

Well, I live in Austin now, so *shrug*