Just read an interesting article about the vertical farm, a proposed way for densely populated cities to feed their population and reduce the carbon footprint of its food supply in the process: http://greenprophet.com/2009/03/02/7250/skyscraper-farming/
Basically the idea, developed by Dickson Despommier a professor at Columbia University, is to create a 30 story buildling that grows enough food and houses enough livestock to feed 50,000 people year round. It's also supposed to be essentially carbon neutral.
Sounds good too good to be true in a way, but also just sterile and missing the point enough that it will probably work.
Read more at Despommier's website: http://www.verticalfarm.com/