We didn't have adventure playgrounds as such, but....... we did live not far from a functioning coal mine, complete with waste heaps.
There were several "pit ponds" formed, I suspect, from water pumped out of the mine, plus, rainwater which ran down the spoil heaps and collected in the valleys.
We used to make rafts, from pieces of wood, old oil drums, and, in later years, bits of polystyrene foam, and, "sail" across the ponds. We never risked swimming in the ponds, the water was foul. If you were unfortunate enough to fall in, none of your mates would come near you, because of the smell.
The site of the pit is now a nature reserve, I see very few if any children there, when I walk or cycle through.
Another source of "amusement" was a small factory nearby. They manufactured radios, I think. Whatever it was they made, required a sheet metal based with various size holes punched out. The discarded circles of sheet metal, of various sizes say 1" across, to 6" across, and, with extremely sharp edges, were discarded into bins in the yard. We would climb over the fence, fill our pockets with the discarded circles, then, later, amuse ourselves throwing them at trees etc, where the would invariable embed themselves in the trunk.
The game came to an end after several months, when, an off target throw, resulted in a disk embedded in one of my pals forehead. trip to hospital, several stitches, a good hiding for all concerned, from respective fathers, new amusement had to be found.