Parking day spot.A gnome stands guard over a Minneapolis PARK(ing) Day installation.Photo courtesy Sveden via Flickr

In most of the cities around the world, huge swaths of public space are blocked by enormous metal objects. These objects are called personal motor vehicles, or cars.

They squat by the curb, feeling and thinking nothing, and getting in the way of a good game of stickball.

On PARK(ing) Day — which this year is today, Sept. 17 — that changes, if only for a few hours. In some 140 cities around the planet, humans take back some of the parking spaces and use them to create mini parks, where they play games, do art projects, or just sit and chat.

PARK(ing) Day began in 2005, when a group called Rebar set down some sod, a bench, and a tree in one space in San Francisco for two hours, as long as the meter would allow. Their mission: “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 … at least until the meter runs out!”

Last year, people in 21 countries and on 6 continents participated in the event. It’s all DIY, and people are encouraged to do whatever they can dream up (within legal limits). Here’s a glimpse of what it looks like.