As a VERY long term project, I've been working on a model of the Michigan Central depot in Ann Arbor for years. It's now a high-end restaurant, but preserves the flavor it its origins.
The materials are Plexiglass and styrene. Why Plexiglass? It seemed like a good idea at the time. It gives a strong model and is the thickness of the actual walls. I even measured the outside dimensions by hand and have searched for years for construction photos or plans. They don't exist any more. The present owners won't let anybody upstairs or in the basement due to all the HVAC equipment there. Even historic interior shots are rare. Only found one! When will it be done? "Some day".