At its height c. 2900 BC , Uruk probably had 50,000 -- 80,000 residents living in 6 km2 of walled area ; making it the largest city in the world at the time .
At its height c 2900 BC , Uruk probably had 50,000 -- 80,000 residents living in 6 km2 of walled area . It was the largest city in the world at the time .