im working a script to help export out levels to UDK thru Maya. This building was created with Ninja City. It is set up to be modular.. there are 9 modules that make up this building.
Design first, then blockout, http://www.bendarling.net/index.php?page=levels then replace blockout with modular pieces. http://wiki.polycount.com/wiki/Modular_environments
This is the wrong method for a large environment model. Better to use modular approach (if architecture) or tiled-texture texture blending (if a mountain or terrain).