Detroit, Michigan is a prime candidate for urban gardens.
When the economy went downhill, people left Detroit for "Greener Pastures". The result - A city in decay - full of burned out, boarded up, empty houses.
Mayor Dave Bing has developed a plan to encourage concentration of the remaining population in "enclaves" that would be surrounded by green space. What a perfect marriage - A vibrant collection of enclaves surrounded by urban farms and efficient rapid transit to move from spot to spot. Some of the open land could be used for solar and wind based power generation that could feed the local power grid. Empty land could be converted to public gardens, recreational space, and could be criss crossed with walking/running/bicycling paths.
It is a gigantic project and must be managed by dreamers, entrepenures, MBA's, fund raisers, philanthropists, and politicians. It needs a master plan -- any planners want to go to work in a City with Promise"?
Detroit can be a example about how to rebuild a decaying city.