And where is the estimate?Europe's urban population increased a lot. But it increased in a way that started to put it on par with the rest of the world, not ahead. It would also be centuries still before Europe developed Megalopolis on the scale of Beijing, Tenochtitlan (Mexico city was in many ways the first modern European city), Cairo or pre-mongol Baghdad.
Even with all their advancements Europe still tended to suffer terrible food shortages on a scale that wouldn't happen in the rest of the world until the early modern era.
Why do you ignore the 2+mil Rome, that existed a thousand of Years before the start of the game?
Mega sities generally acces the size of the country, and almost nothing else.
Basing andvancement of agriculture on food shortages is hilarious, especially considering that wellfare was not the point of European states back than.