The structure of the classic earthship, designed by Michael Reynolds and his company Solar Survival Architecture (SSA), consists of two parts: U-shaped living spaces or earthship rooms, and an environmental interface corridor oriented to the sun (see drawing). The Us are shaped by packed and plastered tires, but the rooms can be closed off if desired for privacy. Flanking the building are two large water-storage cisterns that can hold up to 10,000 gallons of water. The front corridor houses the solar hot water and water purification systems; battery storage for the photovoltaic system; the kitchen and bathrooms; along with the planters that purify waste-water from sinks, showers and bathtubs (Chiras, 2000).