An earth-sheltered house is generally set into a south-facing slope.  Windows on the south let in the winter sun; earth on the other three sides, as well as above and below the house, contributes to energy efficiency. Such a house usually occupies a lot by itself.  Could a similar arrangement be used for high-density housing on level ground, such as condominiums? (TEXT CONTINUED BELOW) Refer to the north-south section at the bottom of this drawing.  The lowest level alternates parking-garage lanes (running east and west) with blocks of bedrooms and utilities, which are connected to south-facing living rooms on the level above.  The living rooms are covered with earth banked around the edges and on the roofs.  On the plan above, you can see that this results in a checkerboard pattern of mounds, all facing south. Skylights in the lawn, indicated by lower-case letters, illuminate the bedrooms below.  There's also stairway access between the lower level and the lawn.