City States evolved to protect the Agricultural domains. Most were controlled by kings or ruling elites but were highly influenced by a priestly class who legitimized their existence by claiming direct (or feigning) contact with the gods. Mesopotamia (the land between the rivers ie. The Tigris and the Euphrates) was the earliest one of these city state civilizations to flourish and together with the Egyptian Nile based culture most impacted the Western World.
The earliest Mesopotamian city was Ur that appeared to have been founded as early as 6500 BC and abandoned about 500 BC. It was located in the flood rich South Mesopotamian. Like the other cities of the time it was surrounded by a wall, had roads and streets and a sewer system. It prospered greatly during a time when all sea traffic entering Mesopotamia had to pass through this port city. Ur’s greatest ruler was the king Ur-Nammu who ruled between 2047 and 2030 BC. He built the famous ziggarut (massive raised structure that resembles a step pyramid with its terrace like form), many temples and improved on the region’s irrigation system.
At the height of its power Ur’s population was estimated to be around 65,000. However this dropped substantially following periods of droughts and sacking by nomad groups. By 500 BC it was abandoned as power in the region shifted to the Northern Mesopotamian city of Babylonia. Nevertheless Ur features prominently in Biblical history. In the Book of Genesis Ur Kadashim is identified as the birthplace of Abraham and it is mentioned in Nehemiah as well. Ur was not the only Mesopotamian city of note. Eridu, Lagash, Nippur, Sippar and Uruk also played key roles in the regional history.