When the organizers of the 1962 Seattle World’s Fair imagined the future, they probably didn’t envision, among the jet packs and routine space travel, tomatoes growing on the roof of a parking garage.

But 50 years later, that’s exactly what’s about to happen a few blocks from the Space Needle, where residents are building a 30,000-square-foot community garden atop a two-story structure once intended for fair visitors’ cars.

The UpGarden has shoestring budget of $4 per square foot – and it’s designed to be built and maintained almost entirely by volunteers.