One of the larger Sumerian cities may have had 80,000 residents.
The origins of Sumerian civilization in Mesopotamia are still debated today, but archaeological evidence indicates that they established roughly a dozen city-states by the fourth millennium B.C. These usually consisted of a walled metropolis dominated by a ziggurat—the tiered, pyramid-like temples associated with the Sumerian religion. Homes were constructed from bundled marsh reeds or mud bricks, and complex irrigation canals were dug to harness the silt-laden waters of the Tigris and Euphrates for farming. Major Sumerian city-states included Eridu, Ur, Nippur, Lagash and Kish, but one of the oldest and most sprawling was Uruk, a thriving trading hub that boasted six miles of defensive walls and a population of between 40,000 and 80,000. At its peak around 2800 B.C., it was most likely the largest city in the world.