From the organizers of PARK(ing) Day Philadelphia:
The number of parks throughout Philadelphia increases dramatically each year on the third Friday in September, when activists, artists, architects, and other citizens transform metered parking spaces into temporary public parks. Known as PARKing) Day, this annual event re-imagines the possibilities of 170 square feet of public space. The event celebrates parks and other public spaces in cities across the country, and raises awareness of the need for more pedestrian-friendly spaces in our urban areas.
PARK(ing) Day was founded by Rebar, a San Francisco art and design studio, in 2005 to raise awareness of the need for green spaces in urban environments. Philadelphia celebrated PARK(ing) Day for the first time in 2008 with over 25 installations for relaxing, cycling, creating art, education, and socializing.
Read more on the PARK(ing) Day Philadelphia site here.