What city and why became the main one in the Ancient Mesopotamia?

The main city of the Ancient Mesopotamia was Babylon. It arose no later than the 3rd millennium BC. Babylon is characterized by highly developed architecture and culture. The city reached its heyday during the reign of Hammurabi, who expanded the borders of the state by annexing neighboring states. The population of the city was engaged in agriculture, traded in various metals, wool, wood, etc. Hammurabi issued a Code of Laws, according to which the Babylonians lived, worked, entered into marriages, sued, etc. When Nebuchadnezzar 2 came to power, the city was built up with temples and palaces. One of the wonders of the world – the Hanging Gardens of Babylon also appeared under Nebuchadnezzar.