It wouldn't be TreeHugger if we didn't have a prefab, and in fact you can order up a prefabricated earth-sheltered Hobbit House from Colombian company Colfibrex. . They well deliver lightweight fiberglass reinforced plastic shells that are bolted together in hours; all you add is dirt and planting. "Advanced engineering, twenty-first century architecture and interior design, with that touch of magic that you wish for." Love the video.