Maybe it's because I have kids, but I definitely think of my garden as playground central. Barbara Butler thinks that way too--you can tell by the elaborate play structures she creates. This one, for Will Smith and Jada Pinkett-Smith's children, is called the Storybook Playhouse. It is elaborately hand-carved with a menagerie of delightful creatures that frolic and play on all four walls, and you can choose your own color palette and one of three sizes. On Barbara's web site
you can also buy plans for garden play houses--but you need a carpenter or carpentry skills to build them.