For three summers in a row, my buddies and me built little forts out of scrap plywood, 2 x 4s, etc. and then we’d spend hours just hanging out in them. The last one was in a tree and was the largest with tar paper on the roof and a hatch in the floor. One day, the ladder disappeared, and then a week later somebody took an axe to it.
Yep, tree forts were the shit :)