"NYC DOT and our partners are proud to present Summer Streets. We will temporarily close Park Avenue and connecting streets from the Brooklyn Bridge to Central Park to motor vehicles and open it up to people on three consecutive Saturdays in August (August 9, 16, & 23)."
The route, pictured (sort of).
Cambridge, Mass does this with Memorial Drive along the Charles, every Sunday basically for the entirety of daylight savings, as do other places, and it's a nice hopeful promise of what life will be like once cars are extinct. Of course it'll be a massive clusterfuck if you're trying to bike, but what the hell.