We made tree house forts. Waaay up. You nail boards to the tree for your ladder, pass wood up to the top guy to nail level, then everybody sits in it. We lived. We rode mini bikes at 30 MPH without helmets. We lived. We made bombs with our chemistry sets. We lived. We jumped off of 20 foot high cliffs into a lake. We lived. I rode up the steps and thru the school on my friends motorcycle without helmets. My Dad, an Army DI, sent me to military academy. I still lived.
Have a scar on my knee from when I fell out of a treehouse while attempting to electrify it with an extension cord from the garage. A kid ran into the cord, clothes lining himself and yanking me out of the tree. We just dusted off and tried again, which is why I got a scar instead of stitches. The lights and radio in the tree were really cool!
The kids over on the next street (just one house over through the backyards) built one in the top of a spindly pine tree (lots of branches only needed a few boards to get to the first branch). 3 or 4 of us could get up there and get that thing to rocking back and forth way over. Lots of fun until one day their MOM caught us.
Same yard where I found out getting shot with a BB gun won't kill ya. Smarts right good but won't killya.