By 3000 BC, Mesopotamia was firmly under the control of the Sumerian people. Sumer contained several decentralized city-states including Eridu, Nippur, Lagash, Uruk, Kish and Ur. The most prominent city of Sumer was Uruk, which is situated around 30 km east of the modern city of Samawah in Iraq. Among the first cities in the region, it played a leading role in urbanization and state formation in Mesopotamia during what is known as the Uruk period. Uruk’s growth made it the largest Mesopotamian settlement, in both population and area. At its height, around 2900 BC, it had a population between 40,000 and 80,000 living in 6 km2 of walled area. This made Uruk most likely the largest city in the world at the time.