My uncle built a house that was more-or-less underground out in California (near Atascadero). IIRC, it was about 200 feet long by 30 feet wide. The only part that was out of the dirt were the windows on the front. The house was roughly shaped like a trapezoid, with the long side being the back, directly into the side of a hill. The short side parallel to the back was the living room, dining room, and at least one guest bedroom and a bathroom, while the offset sides were the master bedroom suite at one end and the kitchen/breakfast nook at the other end.
(That is, say the living room looked west. The master bedroom faced northwest and the kitchen faced southwest.)
The whole back side that was directly into the hill was about 4-5 feet wide, and ran the length of the house, divided into separate areas about 8-10 feet long. These were storage/utility areas such as closets, pantries, and laundry area. The main hallway ran from one end to the other, alongside the doors to the storage/utility areas.
At one end, he had a garage for 2-3 cars, and at the other end, he had a garage that had higher doors and ceilings so he could store his backhoe and other construction vehicles during the winter. The garage at that end was tall enough to have a basketball net on the inside.
He built the house out of cinder blocks, with huge steel beams for roof support. The back walls and side walls consisted of a double set of cinder blocks with a moisture barrier between them, and the back walls may have even been a triple-set, but I could be wrong there.
The roof consisted of dirt and the whole house blended into the hillside beautifully.
I visited the house only once, about 2 years after it had been built, and went through the entire place in awe. Even in the storage areas, there was absolutely no smell of dirt or moisture. The area he lived in is not considered a desert area, and is pretty close to the Pacific ocean.
He was quite proud of his house. He said the reason most people who built houses into hillsides had problems is because they built a residential building underground, which was bound to cause problems. However, he solved the problem by building a commercial building underground. As far as I know, he never had problems with it.
It was quite a masterpiece.