Mesopotamia was made up of many independent city-states, each with their own government and laws. The city-states were either part of the Sumerian culture in southern Mesopotamia or the Akkadian culture in the north. The Akkadian king Sargon I conquered Sumeria to create the world's first empire. Hammurabi, king of Babylon, established a famous code of written laws to maintain order. Mesopotamians had a polytheistic religion and built ziggurats to worship gods like Anu, Enlil, Enki, and Ninhursag who were associated with natural elements.