The Sumerian civilization was the earliest known civilization located in southern Mesopotamia between approximately 4000-2000 BC. Some of the key aspects of Sumerian civilization included the development of cities like Ur and Uruk centered around temples to gods. Religion played a major role in Sumerian society, with kings seen as agents of the gods. Sumerians also developed systems of writing, agriculture, and a currency system that facilitated extensive trade networks. Their art and architecture featured sculptures and temples made from local materials like clay and wood.