Yep, those are the tinny screams of children you’re hearing at Alice Chalmers Playground — And no need to sound the alarm. You’d swear too that those were the smoothest slides you’ve ever ridden. Alice Chalmers Playground is a long-awaited overhaul for Longfellow Elementary, a public school in San Francisco’s Crocker-Amazon neighborhood.

Tucked away from the city’s tech hubbub lies a microcosm of the California landscape. Modular concrete blocks mimic the rocky, rugged coastline of the West. You may even need to clamber through them to reach the heights of the large prefabricated fort structure, the first of its kind in the world. The top of the promontory gives access to a roofline prospect of the neighborhood and, peering down, the dizzying spinning bowl, the throwback sandlot in the corner and the funky-shaped benches sprinkled throughout. Don’t stare for too long, though; the kids are looking up, holding onto the netting below, waiting to slide back down.