Architect and playground builder Ron King is part of a robust movement to bring back more natural play, with environments that serve up some messiness and risk-taking along with exercise.

Kids may play on equipment for a short time, he said, “but then they want to run around. They want to climb a hill, scramble over rocks, listen to the wind and play in the rain. They want to explore and discover rather than have their play experience defined by a piece of equipment.”

So when his company, the Concord, N.H.-based Natural Playgrounds, builds a playground for a school or community, he tries to incorporate any equipment into the existing landscape, using or adding boulders, wooden beams, hammocks, water pumps or sand. Polycarbonate slides are built into embankments so the slides can be higher but the falls aren’t as dangerous. They’re also treated so static electricity doesn’t interfere with cochlear implants, and they’re heat-resistant.