Approaching on a grey, rainy April day, Plas Madoc doesn't look too promising. An estate of 850 houses, seven miles from Wrexham in north Wales, it features high on the Welsh Index of Multiple Deprivation and has been known locally as Cardboard City and Smack Madoc. There's one shop for all the residents. The leisure centre – a shining light with its "lagoon", climbing wall, squash courts and trampoline – has just shut down because of cuts in funding.

But there is something. If you know your way through the maze, you can find a fenced-off grassy area marked with a sign that reads, "The Land. A Space Full of Possibilities." Go through the gate and your first thought may well be that it's a junkyard. In a space 55m squared, with a brook running through it, you'll see piles of pallets, a tonne of tyres, the odd upside-down boat, wheelbarrows, ladders, fishing nets, various stray hammers (courtesy of Poundland), ropes and punch bags.

Children learn about risk through the freedom to play at the Land

Look again and you may notice that the pallets have been organised into a web of mini walkways with entrances and exits way too small for adults. (It's called the Shanty Town and, like everything here, it's temporary. Any child is more than welcome to come along with a hammer and smash it to smithereens.) There's a small, red-headed boy swinging from a tree on a rope across the brook. In a far corner, children are sawing and banging, building a den around a tree. Another girl has a hose – she's filling a canoe with water, just for the hell of it. A teenage boy sits in a shopping trolley, which two mates push precariously up an incline. Some other boys are ripping sheets of wallpaper to build a fire. It's a playground, but not as we know it.



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The Land has put Plas Madoc on the map for the right reasons. It's the subject of a fly on the wall documentary by the American filmmaker Erin Davis, who spent a month filming here last Easter. (It will be released later this year.) Play workers from across the globe have travelled here for inspiration. The playground manager, Claire Griffiths, fields inquiries every day from people eager to start similar schemes. This morning, there was an email from Holland.

Griffiths, a Plas Madoc resident, opened the Land two years ago. A mother of two teenagers, her first job was childcare, then she was "bitten by the play work bug".

"I loved giving children a space where they could just be children, where they could try and fail without being judged or assessed," she says. Her funding from Welsh government initiatives was for an adventure playground and to research it, Griffiths and fellow playworker Dave Bullough piled some kids into a minibus and visited as many as possible around the UK.

"Most are the same," says Griffiths. "American swings, big slides. What happens after 20 visits when the kids get bored?" Bullough nods. "Sometimes the first thing you see when you arrive is a sign saying, 'Don't damage the structures.' Those huge wooden masterpieces with walkways three miles long are the result of adult men playing. They're not seeing it through a child's eyes."

Griffiths and Bullough wanted a space where the children were the masters.

"I didn't have a "vision" of it because that takes it away from the kids," Griffiths says, "but I wanted it to be in a constant state of change using stuff that's scrounged or donated and of no monetary value. Kids are attracted to the novel and new. In the past, they could disappear all day in search of it. They could find adventure, test their limits. We don't let kids do that any more.

"I wanted to compensate for the lack of wild play and 'adult-free' experiences. I wanted something kids could make up and break up and rediscover every visit."

Danger was another draw. Here, children could assess risks themselves whether by climbing a tree, sawing a slab of wood or building fires. Three playworkers are always on site – but their role is as helpers not teachers, and certainly not police. There are no rules as such. "For a fire, you basically need a member of staff and a bucket of water," says Griffiths. "The kids kind of self-police it. They have learned how to light it, put it out, and if someone tries to throw on something that won't burn, they'll stop them."

Ironically, the playground was recently shut down by an arson attack. It was actually closed when Griffiths received a call from neighbours concerned by the abnormal level of flames and smoke. The youths responsible have been picked up by police – and were not Land users.

Claire Griffiths, who set up the Land: 'I loved giving children a space where the could try and fail without being judged or assessed.'

In fact, the Land is close to the original adventure playgrounds that started in Denmark during the second world war. The first was created by the landscape architect Carl Theodor Sørensen after watching children playing on bombsites, building and demolishing. It opened in Copenhagen in August 1943 and was known as a skrammellegepladsen, which translates as "junk playground". Nothing was static or expensive – it was all wood, rope, empty vehicles, bricks and logs, and the children had the power to create their own world. Three years later, the English landscape architect Lady Allen of Hurtwood, happened to see it during a lecture tour and brought the idea back to Britain. The first adventure playground opened in Camberwell, south London in 1948. They soon spread to Liverpool, Bristol, Grimsby and throughout the UK.

When the day came for the Land to open in February 2012, Griffiths admits to feeling nervous. "It was a risk," she says. "Maybe the kids would run in and say, 'Where's the zip wire?' But they got it straight away."

It was the parents who needed to be persuaded. Wayne Greenshields grew up on Plas Madoc and is a single father to James, nine, and Taylor, six. He's here today while his boys scale trees like squirrels. "They love it here, it's dead dangerous!" he says. "But I had to be converted. I couldn't see the benefit of kids playing with hammers, saws, mud, fire and water. I thought they should be happy as Larry playing on the computer or in a 5x3ft yard while I chatted to my mates."

Wayne Greenshields was then persuaded to attend a course organised by Griffiths called Parents Learning to Play. "She had us playing tig and God knows what. She organised an egg fight and no one wanted to do it. By the end, we were gutted when there were no eggs left! On the first day I came here, James climbed a tree really high. I was petrified because everyone was telling him to jump. He looked down and said, 'It'd hurt from here', climbed a bit lower and then jumped.

"That was a little risk assessment right there. Kids learn if we let them. The other day, we were here and I was cutting a piece of wood. Taylor shouted, 'Dad, your hand's too close to the saw!' He's only six."

When James comes over, I ask for one of his best memories of playing here. "Once, me and my cousin built a two-storey house," he says. "We found a mattress for the bedroom, a real bath for the bathroom, we had a sofa in the living room with a real fire. In the kitchen, we had a bench and we made washer-driers with boxes and tyres for the circles. It took the whole day."

Ellie and Sian, both 11, are also regulars. Their most treasured memory is one day last summer when all the children created a water slide coming off the roof of the office with mattresses at the bottom. "The best things here are the fights," says Sian. "Water fights, snow fights, chasing people with hammers …"

There have been no injuries so far, beyond the odd twisted ankle – though everyone knows it's a possibility. "We're not saying it won't happen, bones may well be broken," says Bullough. "Better a broken bone than a broken spirit." Every aspect of the Land has to pass a complicated risk-benefit assessment (the risk benefit for fire runs to nine pages). But the underlying ethos is that children have a strong survival instinct. Here, they weigh up danger, test it out – and have fun.

There are other gems like the Land hidden round the UK. One is Glamis Road in the deprived east London borough of Tower Hamlets. On an equally unpromising patch of land overlooked by tall tower block housing, it's a wonderland of wooden structures, tunnels and slides – many movable, more dubious and dangerous than anything Disney can dream up. Here a girl sits poking a small fire while a foot away, a boy hammers at a nail. There's a bike workshop, piles of junk, mountains of woodchip. It's surprising how fast the unthinkable becomes normalised in this magical, alternative universe. After an afternoon narrowly escaping injury and having the time of her life, my eight-year-old daughter emerges from the den she's making (inside a tunnel, which doubles up as a slide) yelling, "I need a saw!" Somehow, it seems entirely appropriate that she is given one.

"People forget that kids have a sense of self-preservation like we all do," says Paul Hocker of London Play, a kind of play thinktank. "We need to trust them a bit more. I was in the Gambia recently and they had six year olds with machetes cutting down the bush! We're raising a generation who have never been allowed to test themselves."

Though a "junk playground" shouldn't cost too much to create, the maintenance and the playworkers are beyond most budgets. Glamis Road, which started in the 60s, is struggling to stay open. "If you rely on the Local Authorities to fulfil their 'play quota', you'll get the low maintenance, low fun option," says Hocker. "The voluntary sector leads the way."

London Play's revival of Play Streets is one innovative example – which uses 1938 legislation to shut down streets on a regular basis for the children to reclaim. In the 60s, there were 200 Play Streets across London. Boroughs reopening them in the city include Islington, Westminster, Hackney, Haringey and Lambeth.

Back in Plas Madoc, Griffiths is also adamant that the Land should not be the children's only option. She has knocked on every door of the estate and spoken to residents, encouraging them to reminisce about how they played as youngsters. They agreed to become a Play Priority Area – the signs are on walls to remind everyone – and Griffiths and her team spend as much time leading street play as they do in the Land, organising games of man hunt, turning up on doorsteps with random play objects.

"Play should be everywhere – a natural part of life," says Griffiths. "The Land is fantastic – but in an ideal world, there wouldn't be a fence round it. Children would be able to do all the things they do there – without having to open and close a gate."

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• This article was updated on 12 May 2014 to replace the video clip of 'The Importance of Playing with Fire (Literally)'