Check out the photos over there. SF writes:

This neighborhood is full of greenery — majestic old-growth trees and beautiful landscaping — but it’s all private property. We are seriously lacking in community gardens, all-age recreational facilities, and public parks closer than the Parade Ground and Prospect Park (more than a mile away for many of us). The Tot Lot on Argyle Road is popular with kids and parents (as one parent mentioned to me yesterday, it’s so full that “the kids are on top of each other”), but there are very few options for older kids or unaccompanied grown-ups. So Park(ing) Day — an international event, co-sponsored in NYC by Transportation Alternatives, The Open Planning Project, and the Trust for Public Land — seemed the perfect opportunity to create a public park for everyone.

We built it, and they came: a public space with real grass, trees, art supplies, games, wi-fi, and live music.