One of my most fun experiences was in a tree, at a park, with people walking underneath. (If you're interested in the mechanics, I sat on a thick branch with my back against the trunk. She sat on me. ) The tree was very leafy, so I doubt that anyone looking up would have actually seen all that much. Problem is, we couldn't stop giggling. Fortunately, we were finished and relatively put back together before this boy decided to come see what the fun was!

On the other hand, I strongly recommend you avoid trampolines. It's a quick way to learn a whole new definition for "getting bent". OUCH!