I roamed the back streets of the inner suburbs as a child, explored drains only to be startled by water rats. I explored forests and hiked mountain trails, alone and with other kids of the same age. Once I got stuck half way up a cliff and was too scored to climb to the top and far too frightened to go back the may I'd come.
Well, I'm here now, and in my seventies, so I must have broken out of the inertia of fear and made a decision. Time blocks out what that desision was, but based on my current behaviour when I'm in dangerous waters I'd choose the devil I know I can tackle, over one I fear will beat me—at least until I've developed more skill. I'm not a quitter; I guess that's why I didn't die half-way up a cliff face, or fall off it in fatigue. Tough life lesson. I don't recommend other children trying it.
It was always strictly forbidden to play down at the creek, or in the river, without adults, but on a really hot day we could never resist the lure of the water. Oh, and trees, walls, and cliffs were made to be climbed.
We created dug-out hideaways and tree houses, on undeveloped land. As long as I was home before dark I (born in 1946, as one of the earliest baby boomers) was allowed to explore anywhere.