In the Silo? If I ever have land, I'm going to build a few of these for my kids as they become young adults but aren't ready to go into debt for a place of their own. They can go live in a drain pipe out back for awhile.
Pondless Backyard Fountain Pond and Waterfall. Even without the fountain, which in Az will grow algae like nobody's business, I think the idea of softening up the patio with a little rock garden with plants mixed in.