Something which should exist, but (as far as I know) doesn’t: parks cultivated specifically to provide trees for climbing.
We have elaborate topiary — but only with the aim of looking pretty. It would presumably be easy to cultivate trees with convenient bends, branches at arm-height, and all the stuff you’d want to make a nice climbing tree. You’d need many decades for them to grow up. After that, though, you’d have a fantastic and pretty place.
Presumably it would currently be an insurance nightmare to do this. But that wouldn’t have been the case 50 or 100 years ago. So why aren’t there tree-climbing parks?
[This partly triggered by Aaron Swartz’s plea to replace spectacles with experiences:
The world is weirdly disappointing that way. Billions of dollars are spent making and watching people explore mysterious tunnels, chase down alleys, and fly as if by magic, but there’s hardly a single opportunity to actually do any of these things.