Retaining wall?
Yup. The backyard cuts into the hill and the retaining wall consists of two 6 foot high walls, with the upper wall set back 9 feet from the lower wall to create a shelf. The solar pool heaters (black panels) occupy half that shelf. We'll eventually get around to putting some large potted plants on the rest of it.
The retaining wall was not originally planned - we had originally hoped to put the house at the top of the hill, but the geology wouldn't cooperate.
As it turns out, we're glad they cut us into the hill because someone built a house right behind us and that retaining wall gives us privacy. The wall also seems to act as a venturi and cause a breeze to pass through the backyard almost all the time, which is nice.
You can get a better idea from this photo:
Christians warn us about the anti-christ for 2,000 years, and when he shows up, they buy a bible from him.
