The key feature of the ancient Mesopotamian city-states was their urbanization, with each city functioning as an independent entity often comprising a central temple, a palace, and various public buildings surrounded by agricultural land. These city-states, such as Ur, Babylon, and Eridu, had distinct governance structures, typically ruled by a king or a priest. They developed advanced systems of writing (cuneiform), law, and trade, facilitating communication and economic exchanges. The city-states also engaged in frequent conflicts over resources and trade routes. Their cultural and technological innovations laid the foundation for future civilizations.