According to Official Guinness Records,
Dating back to around 3200 BC, the world’s first city was Uruk, located in southern Mesopotamia (modern Iraq). Home to some 50,000 inhabitants, it was the largest settlement of its time, covering 450 hectares (1,112 acres) and encircled by a 9.5-km (5.9-mi) city wall. Thriving as a result of trade and agriculture, Uruk also became a great artistic centre, featuring many elaborate mosaics and monuments.
For a complete list of 3200 records, please visit 3200 Guinness Records in Iraq.