"May I make a plea for a greater use of things as they are? The original valley was attractive and would have given more area for play...Here was a natural bird retreat, which has now a bird house--a good thing in itself, of course, but why destroy the natural to gain the artificial?
This valley was a natural walk and a few years ago might have been made into a pleasing gateway to the park. It would have wound by the brookside where one could enjoy the wild plants....Let us get away from the obsession that we must artificialize the entire play areas."
"Mother Nature's Invitation", by William G. Vinal, in The Playground Magazine, March, 1926.
It would appear that natural playgrounds are hardly a new idea.
[text from the online archives of the Library of Congress, photo from the flickr photostream of Tim Gill. 'Richmond Park in West London: one of the capital's royal parks, where the rangers appear relaxed about den and shelter building']