The Sumerians can be considered the first people, according to historians, to reach the level of civilization. They lived around the fourth millennium BC. Sumerian civilization is classified as an urban type, since it consisted of several independent city-states. The most significant of them are Lugash, Ur, Eridu, Uruk, Umma, Akkad, Nippur and Sippar. All these cities were located in the Mesopotamia region.
It is known that the Sumerians had knowledge about the structure of the solar system, knew ternary counting, and had ideas about the origin of intelligent life. Due to constant wars between city-states, the Sumerian culture weakened significantly. Around 2000 BC, this ancient civilization fell into decline.