Park(ing) Day, an international event in which metered parking spaces are converted into into temporary parks, returns to Chicago tomorrow for its third year. The project began in San Francisco in 2005 when the design company Rebar created a park (complete with sod) in a single parking space for two hours. The goal is “to call attention to the need for more urban open space, to generate critical debate around how public space is created and allocated, and to improve the quality of urban human habitat.”