Ancient Rome grew beyond 1 million inhabitants in the 2d century. Chang'an (Xi'an), China in the 8th century, Bagdad around the 10th century. There were big cit

Ancient Rome grew beyond 1 million inhabitants in the 2d century. Chang'an (Xi'an), China in the 8th century, Bagdad around the 10th century. There were big cities before. https://en.wikipedia.org/wiki/List_of_largest_cities_throughout_history https://en.wikipedia.org/wiki/List_of_largest_cities_through...