The main building material of ancient Sumerians was mudbrick. Mudbrick is a building material made from a mixture of clay, silt, sand, and water. It is typically formed into bricks by hand or by machine, and then dried in the sun or fired in a kiln. Mudbrick was used extensively by the ancient Sumerians because it was cheap and easy to obtain, and it was also well-suited to the hot and dry climate of Mesopotamia.