In constructing tombs to outlast eternity, the Sinai nomads used an architectural technique called corbeling. The outer wall of the nawamis was built straight up to a height of about 6 feet. The inner wall, however, was corbeled; that is, each course of stones jutted slightly more toward the center of the structure, forming a partial dome, which was crowned with a capstone. The spaces between the walls were filled with rubble, strengthening the structure and creating the distinctive concave shape of the roof.