Would you live in a house made of dirt? The answer, I'm guessing, is no. As a building material, dirt has an image problem. Mud dwellings are practically synonymous with third-world poverty. At best, an earth structure is something you expect to encounter in an old hippie compound. Yet some of the world's most magnificent structures are made of little more than dirt and water, from New Mexico's pueblos to the great Djinguereber mosque in Timbuktu.