The answer is the Sumerian city of Uruk.
Uruk was the first city in the world that became a large commercial and administrative center.
The city was founded over 3,500 BC and it's most powerful has between 50,000 to 80,000 living in its 6km2 walls.
At the time, it was by far the largest city in the world and a unique human settlement of its kind with proper governing laws, administration and a huge commercial center. They also feature the first instance of the construction of monuments by humans.
Uruk is located in modern-day Iraq.