The master bathroom has a small window and a large skylight above the shower—and shares a translucent glass expanse with the kitchen, where it becomes the backsplash. "Even though it’s a buried room," Don says, "we have three sources of natural light. For the shower, we made a very high curb so you can stop up the drain and turn it into a big soaking tub. We used white, one-by-four-inch or one-by-six-inch Carrara marble tiles from Royal Stone and Tile. They come on a 12-by-12-inch sheet. I got the small tiles because you can use them to work the bottom plane into the shower."