http://singularityhub.com/2012/11/05...vertical-farm/

And going from theoretical test to "actually working right now."

Singapore, a small country that imports most of its food, has now begun selling vegetables from its first vertical farm. And even while they’re more expensive the vegetables are already selling faster than they can be grown. If the farms prove sustainable – both technologically and economically – they could provide a much desired supplement to Singapore’s locally grown food and serve as a model for farming in other land-challenged areas.
According to the article, it's not just land-efficient, it's also water and electrical efficient. I could see this being a great boon. Imagine, cities being self-sustaining rather than dependent on long distance shipping and transport.

Fingers crossed for this farm and the company making it.