Fountain: How to Build a Concrete Fountain, Create a stone-lined garden pond, then carve a waterfall out of a block of stone using basic power and hand tools. The technique is simple, even for beginners.
Something a bit more elaborate than this leading up to our moon living room window? I could tie it into the tree-house theme I'm thinking of doing. It could just look like a platform tree house at the top of the "tree".