Something had always marred the view from Mimi Jensen and George Elbaum's family room: it was the black tar-and-crushed granite roof of their garage. Then Jensen saw a depression in the gravel and the shadow it cast. "A light went on," she says. "I had played with desktop Zen gardens. I thought, Why not make the roof a big Zen garden?"

She turned to landscape designer John McRae for help. He covered the roof with a new layer of gravel and used lightweight urethane and polyurethane rock look-alikes as accent pieces. He creates patterns with his hands. "To keep it interesting, I rake in a new pattern and rearrange rocks a couple of times a year," says McRae.