Back in the 70's, my father brought back a *giant* box from some industrial refrigeration unit or something. It was like 4x12x6 or so. He made a giant playhouse that me and my sister played in for years.Totally awesome, we drew on the walls, cut out secret exits, strong enough to play on the roof. Go figure, couple of kids with a giant box, awesome!

Damn, everybody beat me to it.
--
YT

Ah, memories... back when I was in like pre-school/first grade , my father brought home a giant box from work, like industrial air conditioner box or something. He turned it into a house in our basement. Were talking 6' x 12' with pitched roof, doors and windows... My sister and I played in that thing forever. Every kid should have one.

Wow, it's 7th grade again. I can hardly wait!