### ArchitectureThe Tigris-Euphrates plain lacked minerals and trees. Sumerian structures were made of plano-convex mudbrick, not fixed with mortar or cement. Mud-brick buildings eventually deteriorate, so they were periodically destroyed, leveled, and rebuilt on the same spot. This constant rebuilding gradually raised the level of cities, which thus came to be elevated above the surrounding plain. The resultant hills, known as tells, are found throughout the ancient Near East. According to Archibald Sayce, the primitive pictograms of the early Sumerian (i.e. Uruk) era suggest that "Stone was scarce, but was already cut into blocks and seals. Brick was the ordinary building material, and with it cities, forts, temples and houses were constructed. The city was provided with towers and stood on an artificial platform ; the house also had a tower-like appearance. It was provided with a door which turned on a hinge, and could be opened with a sort of key ; the city gate was on a larger scale, and seems to have been double. The foundation stones - or rather bricks - of a house were consecrated by certain objects that were deposited under them." The most impressive and famous of Sumerian buildings are the ziggurats, large layered platforms which supported temples. Some scholars have theorized that these structures might have been the basis of the Tower of Babel described in Genesis. Sumerian cylinder seals also depict houses built from reeds not unlike those built by the Marsh Arabs of Southern Iraq until as recently as 400 AD. The Sumerians also developed the arch, which enabled them to develop a strong type of roof called a dome. They built this by constructing several arches. Sumerian temples and palaces made use of more advanced materials and techniques, such as buttresses, recesses, half columns, and clay nails. MathematicsThe Sumerians developed a complex system of metrology c. 4000 BC. This metrology advanced resulting in the creation of arithmetic, geometry, and algebra. From 2600 BC onwards, the Sumerians wrote multiplication tables on clay tablets and dealt withgeometrical exercises and division problems. The earliest traces of the Babylonian numerals also date back to this period. The period 2700–2300 BC saw the first appearance of the abacus, and a table of successive columns which delimited the successive orders of magnitude of their sexagesimal number system. The Sumerians were the first to use a place value numeral system. There is also anecdotal evidence the Sumerians may have used a type of slide rule in astronomical calculations. They were the first to find the area of a triangle and the volume of a cube. |