In the 1960s, urban decay set in from failed public housing projects and demographic shifts.

WSJ: Battle of the Beach

No one would be rash enough to claim that these measures will cure urban decay.

ECONOMIST: The pre-budget report

This particular block is a slum, one where we can see urban decay take place in real time.

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Detroit could be the city to buck this trend, with its well-documented urban decay, its abundant broken windows.

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Housing stock is crumbling, and the center city is a study in urban decay: empty lots, boarded-up businesses, foreclosure signs.

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Students bring in money, and the bohemian nature of the city also attracts artists and architects who have helped transform the urban decay into something beautiful.

BBC: Living in: Great university towns

The city has long been synonymous with urban decay.

ECONOMIST: The mayor has a practical vision for a long-neglected city

Urban Decay, for example, distinguishes itself with often risque product names, including Sin, a champagne-colored eyeshadow, Indecent, a peach blush, and Perversion, a black eyeliner pencil (and those are some of the polite selections).

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After several of New Orleans' public housing projects were damaged in Hurricane Katrina, city officials want to demolish the buildings considered by many to be symbols of urban decay and replace them with mixed-income units.

NPR: New Orleans' Controversial Public Housing Model

And now, four years after Reynolds planted the first illegal seed, a grassroots guerrilla gardening movement has sprouted up around him, with thousands of revolutionaries throughout the world who are armed and ready with rakes and shovels to turn areas of urban decay into springy patches of peonies and sunflowers.

CNN: Guerrilla gardeners green their city on secret moonlit missions