At the Museum of the City of New York, Vincent Cianni’s bracing photos show how a group of teens on Williamsburg’s south side organized to get a skate park built in the shadowy wasteland beneath the Brooklyn-Queens Expressway. If these kids can persuade City Hall to let them shape their own terrain, imagine what five boroughs’-worth of block associations, business improvement districts and Livable Streets advocates can accomplish. Check out the show, We Skate Hardcore, and get the wheels turning. It closes August 6.