here. He uses no nails or glue to make these amazing things! There may be an installation near you! There is one at the Morris Arboretum in Philladelphia (just down the road from my old stomping grounds). I've got to take G there this spring! She will love exploring it. At MA there are also many other cool features, such as the Garden Railway (opening May 29, 2010)and Out on a Limb: a bird's eye view of the place.
For more pictures of PD's work check out Babyology's post.