One of the driving forces for this whole superhero project has been my interest in local architecture, and the idea of creating a custom cityscape for the heroes and gangsters and cops and nazis to fight over. It's taken a lot of trial and error, but I've finally figured out a building process I'm happy with.
The buildings are based on pictures I take around the city, scaled and adjusted in photo software and then printed on foamcore at Fedex.
I cut them out and glue them to a collapsible carton (like you'd use for a sixpack of beer bottles). The bottom of the carton has been sprayed black for a roof, but I may add cardstock for a better fit.
The facades are not glued, but magnetized, so I can have multiple facades for each building depending on the specific setting of an encounter, e.g. fancy vs rundown, commercial vs industrial. The tops of the foamcore are edged with brick-colored play-doh, smooshed into an approximation of coping tiles.
The goal is to have about a dozen buildings of varying heights, one to four stories, a few double-wide, all collapsible so as to fit a whole board's worth into a single case or backpack. I also have O-scale accessories like trash cans and streetlights, 1/56 scale cars from 1st Corps, and eventually some road tiles to put it all on. I also have plans for magnetized signs and awnings for further variety, more on that as it develops.