When I was planning to put the Super Chief on a shelf, Chicago was going to consist of a few small non-descript buildings way off in the distance at the far end. However when the plans changed to a larger layout "in the round" (a 360 degree view) I realized I needed to incorporate more detail, and in scale. The problem was that the only Chicago scenery that I was familiar with was what I saw in one of my favorite movies, "The Blues Brothers."
As with my Terminator-related diorama, I had the DVD and was able to watch the movie and take screen shots of potential layout subjects, including the Plymouth Hotel (with the elevated rail line running very close by), Ray's Music Exchange, the Curl Up and Dye beauty salon, a small church, a few police cars of varying condition and some other tidbits. (If you know those references, you probably like the movie as well.)
Ray's Music Exchange
As always, I started the Chicago portion of the layout with building mock-ups, the first of which was Ray's Music Exchange. The little wood block turned out so well that I decided to make it the first building of the section.
With the screen shots I had taken, and other pictures on line (including an odd, but very helpful Lego version), I was able to design and build a decent looking N scale building.