Alexandria took the lead with 150,000 people by 300 B.C.
Located in Egypt, Alexandria was founded by Alexander the Great in 331 B.C. It quickly became the largest city. It would be the capital of the country for the next 1,000 years.
The Mediterranean city was home to the Lighthouse of Alexandria — one of the tallest buildings in the world — and the Great Library of Alexandria — the biggest in the world.
In addition to Greeks and Egyptians, the city had the largest urban Jewish population in the world.
Alexandria declined during the Roman empire and Muslim conquest.