For my Persian project, I am producing a 3D map of a fictional city in Google Sketchup. It's a bloody big project and will take me aaaaaaages, but I think (hope!) it will be the dog's b****cks when it's finished!

Sketchup is a great free program and dead easy to use. I plan to put some districts/buildings in Photoshop to make them look really nice. I hope to post some WIP soon...