Ancient Sumerian civilization had 8 key features: it consisted of organized cities like Ur and Babylon ruled by kings through a monarchy system; people specialized in jobs like farming, merchants, priests and scribes; there was social stratification of upper, middle and lower classes; they developed art, architecture like ziggurats and statues as well as pottery and poems; they practiced a complex polytheistic religion with many gods; and engaged in public works such as ziggurats, roads, irrigation and schools while also developing one of the earliest systems of writing called cuneiform seen in epic poems like the Epic of Gilgamesh recorded on clay tablets.