Aged 7 or 8, I was away boarding at a school, but most went home at the weekend and only four of us were left at the weekend. We used to amuse ourselves a lot of the time. 

One evening someone decided to go to the gym, which had wall bars, vaulting horse, benches and two thick climbing ropes that hung from the rafters.  We set up an assault course, stripped off and had a great evening enjoying the freedom. Even at that age, we were aware of the feeling of liberation, with the added spice that it was a bit naughty - the gym was out of bounds as I remember.