I always work with weird settings, subterranean, arcology, etc.
I need to figure out how these actually WORK. In this case, it's metro stations (something I've been in all of once or twice in my life. I know I used the metro when I visited London way back when, and I think I may have used the NYC subway). I've seen a few more while watching things like Top Gear and approximations of them in video games. They're a fairly straightforward, utilitarian structure (generally), but it still helps to know a bit more about them before I start building a world around them.
Time for research!