BV, that hedge tunnels one is a work of genius.
My younger brother and I loved this sort of thing and would make them at any opportunity. We could just about squeeze behind the garage (and climb up the fences and sit on the roofs) that was a fort of sorts that was always there.
We also used to construct hugely complicated but temporary ones out of an old ladder we were allowed to play as a climbing frame, and then use bits of wood, blankets and, much to our parents' fury, the nets off the strawberries (this made it army like and was
entirely essential).
As young teenagers my friends and I used to sit in a field down by the railway line, secretly, in the corn (or whatever it was) and were hidden from view by it being too tall. However, I realised we weren't so subtle as I was on the train and saw there was a huge hole in the field, clearly visible.
Later, we found a hole in the brambles by the side of the same field and used to sit in there and do all the secretive things that teenagers do like smoking dodgy Old Holborn rollups and the like.

Twas our special place and we took a few bits and pieces down there to sit on and stuff. Sadly, a while later, my two best friends went there and took a massive and calculated overdose, again, because it was secret and safe and it was our place. (By a series of lucky events, they ended up being ok, and are now splendid twenty-eight year olds that I love to bits.)
A couple of years later I went back (none of us ever had gone back after that) and there was still paracetamol blister packs all over the ground. I don't think anyone else had ever found it. It was really sad and strange to go back and see all that and think of them there doing that by themselves.
Still, thinking about forts whilst writing this makes me think how important they were at all the stages of being a kid there were always somewhere safe where there weren't adults, that you made the choice of how you used it and how it looked.
I actually wonder if a lot of the sheds/workshops/home offices on this earth are really just a fort substitute, where you can hide from the other adult in the house.
