On Tabletop Witchcraft, John builds an amazing gladiatorial coliseum that is one of the most impressive tabletop builds I've seen in a while.
It's also a surprisingly approachable build, if you have a world of patience and time (and ideally a Proxxon hot wire table). Most of it is just foam, toothpicks and skewers, and epoxy putty. He goes through the build step-by-step and even has plans available (US$7).
Image: YouTube