A little more added, and now I'm toying with getting it from Blender into XSI and then into Hammer (or perhaps from Blender to Hammer directly, if I can find a working exporter).
To get under the polycount limit for the XSI Mod Tool, I had to chop up the city into separate models - one for each city block. I should have done this a looong time ago, as it is an amazing help when raising buildings from the ground up, pushing vertices around and soforth.
Full view here (I made it high-res for you guys =D): Media.moddb.com
sooo, why did you make it in XSI and not in hammer?
I too wonder that. I know for HL2 and the ep's they would make a building in hammer (just the general shape) then import it into XSI to give it fine details like cracks and stuff. Seems like a lot of extra work building in XSI, but you do have me intrigued to see how it turns out. Would you mind sharing with us the amount of hours this took?
Actually, I made it in Blender, primarily because I am overwhelmingly more comfortable using Linux than Windows, and because Hammer doesn't have any rotoscoping capabilities, and this is based off a real-world location. The (unrotated) aerial view I'm using is visible here: Moddb.com