I have yet to have visited an adventure playground, although there is one at Mercer Island I am hoping to get to this summer with my twin boys and it sounds as though Teacher Tom offers one at the Woodland Park cooperative a play area that is very close to an adventure playground. In fact I think it was his webpage where I found this link talking about adventure playgrounds. It sounds like there will soon be a movie about these amazing playspaces. In the meantime I continue to work on making our own yard have as many "loose parts" as I can.
It is amazing the creative play that comes from adding elements to the play yard. From scrap wood that becomes forts, bridges, stir sticks and tools- to our Christmas Tree which is in the back yard still drying and preparing for its final use in a bonfire but which currently gets a myriad of attention. For example the other night when we had children over one child just wanted to swing at it with a stick and knock it over. Then stand it up again. Yesterday T asked if he could "prune" it and he began cutting off the boughs. S and I used these to make wreaths around our blueberry bushes. Then both boys decorated the play house with evergreens and made soups for a party out of the needles.
Here is an article that was recently in the Atlantic about Adventure Playgrounds