For a stretch of the later fourth millennium BCE, Uruk was the largest concentration of people anywhere. Its growth is the event that archaeologists name the period after, and what happened at Uruk then set the pattern for Mesopotamian cities afterward: a walled settlement of tens of thousands, a monumental religious precinct at its centre, an administrative class that fed on the surrounding countryside, and mass-produced ration bowls turned out in numbers that imply organised labour paid in grain.
Out of that administration came writing. The oldest substantial body of written material known was found in the Eanna precinct, and it is not literature, law or prayer. It is bookkeeping: counts of animals, of grain, of textiles, of workers, tallied with numerical signs and pictographic word signs impressed on clay. The script that later carried the Gilgamesh epic, Babylonian astronomy and the correspondence of empires began as a way of not being cheated by a granary official.
The city keeps its place in memory long after its power passed. The Sumerian King List brings kingship to Uruk after the flood. Gilgamesh, its most famous king, is a figure of epic before he is anything else, and the poem opens and closes on the walls of Uruk, inviting the listener to inspect the brickwork and judge the man by it. The walls are there. They are among the first things a visitor to the ruin field sees, and they are attributed in the poem to the king whose search for immortality the epic then reports as a failure.