The grandkids in Chicago know public parks like adults know coffee shops. They can always direct us to a park they are sure we will really, really love – you know, a park with swings where we can sail so high we lose lunch, a towering web of interlocking ropes that a recently retired man might want to scale, or a maze of galvanised pipes that a grandma might want to crawl through on her belly.

They recently led us to a new park with a dazzling array of colourful playground structures where concerned parents hovered over children scaling ladders and flying down slides. Other parents ringed the perimeter glued to cell phones, glancing up when they heard a familiar cry.

When a child took a tumble on the cushioned ground cover, parents instantly materialised offering comfort, a sanitised wipe or a juice box. Or all three.

The kids played for a few minutes, yawned and stretched, then asked if we wanted to go to a better park.

Because it had been a good 30 minutes since we last broke a sweat when they led us on a dead run through an empty soccer field, we said, ‘Sure, why not?’

We followed a path that opened to a small grove of trees in an expanse of packed dirt, the centrepiece of which was a huge felled tree trunk.

Near the trunk were piles of stripped branches and small logs. Scattered about were slabs of trunk, wood shavings and an iron pot that must have fallen off a wagon train 200 years ago.

Parents were present, but at a distance. A silent, unmarked barrier warned adults to back off and leave the kids alone.

There were five children, then seven, then eight, a ninth watching from behind a tree. They built a lean-to against the downed tree, dragging limbs and logs into place, giving one another an assist as needed. No one appeared in charge, assuming the role of alpha; they all worked diligently towards a common goal.

There was no consulting computer screens or apps, nobody wore shirts with corporate logos and none of the parents got involved – other than the occasional shout of ‘Ten more minutes, then we go!’

A girl attempting to move a big round slab of wood was no match in size for the task. She couldn’t budge it. But two could. They weaseled a wedge beneath the slab, raised it, stood it on its side and rolled it towards the shelter.

Another child who had been filling the old pot with curled wood shavings dragged the pot to the round wood slab and heaved it on top. The soup was on.

Paediatricians call this the miracle drug. They say this miracle drug gives children opportunity to learn how to collaborate, make decisions, imagine, create and develop confidence. They say children who receive regular doses of this do better in school and better in life.

The miracle drug is play – pure and simple childhood play.