The primary components of an adventure playground are moveable parts (which can include items like boxes, pipes, paint, hammers, and even saws) and trained, paid grown-up “playworkers,” who oversee and facilitate the play without interfering. Children are free to build their own structures, tear them down, climb, graffiti, create. They are encouraged to take calculated risks in order to learn resilience, grit, and problem-solving skills. The concept of vandalism is moot at an adventure playground—it is child-led play in its freest, most anarchic form. It is organized chaos.

Though adventure playgrounds never reached the popularity in the U.S. that they have in the U.K. and Europe, the environmental psychology Ph.D. student Reilly Wilson notes that there were 20 across America in the 1970s, according to a survey of the American Adventure Play Association (an organization that has recently been revived). There were several in New York alone. But without funding to maintain them, the adventure playgrounds fell into disrepair and looked, quite frankly, like the bombed-out remains they were originally based on.

Shifts in parenting trends are reviving interest in waste-material playgrounds. So-called helicopter parenting, in which parents hover and rush in at the first sign of distress, is increasingly being called out by authors and researchers writing books and articles about the importance of letting children fail, working out their own problems, and developing independence. New studies show that we should be letting children engage in riskier play.

Adventure parks benefit parents as well as kids. Wilson, who is also on the board of play:ground NYC and became interested in playgrounds after working as a nanny, posits that adventure playgrounds might help assuage hovering moms and dads. “There’s a lot of social pressure among caregivers to intervene when their kid is making another parent nervous,” she says. “Other adults will step in very quickly so people will preemptively step in so as not to deal with the social pressure.” That pressure is off in a monitored, safe space like an adventure playground, where the culture is to let kids do their own thing.

Marisa Karplus took her sons, ages 3 and 6, to the play:groundNYC pop-up on Governors Island last summer, thinking they’d just stop by then continue on their way. They were all having such a great time that they stayed for three hours. “My husband said that it looked like Burning Man for kids,” she says. “They were happy on their own … It gives [parents] permission to sit back without feeling neglectful.”

Sometimes, though, it takes a bit of reprogramming before parents can loosen the reins. It’s not uncommon to find the occasional sign that says, “Parents! Sit down and relax!”