But actually the house is located on a steep hillside. This patio is grassed in to seem like ground level. Terraces make it seem as if it is on flat ground.

And, in fact, this swimming pool is actually forming a retaining wall at the bottom of the steeply sloping original lot.

The structural Engineers, David H. Lau and David Maynard make the pool do double duty as a bulwark against the  steep site so that a flat lawn can be made behind it.