And, you can build skyscrapers that are a lot more green...
http://www.treehugger.com/files/2006...t_tower_le.php
http://www.nyc-architecture.com/MID/MID124.htm
http://www.ecogeek.org/content/view/695/
I read an article in DWELL magazine a while back about an apartment building in LA that provides all the energy needs for the tenants, because of the way it was designed, and solar panals. (I will try to find the article later so I can cite it for you. but the point is, it CAN be done, even for apartment buildings.)