Many people who take an interest in ancient history naturally wonder what a major city from the distant past would have looked like. Recently, several teams have started to reconstruct the city of Rome during the height of the Roman Empire with high fidelity. I like the videos below and may be adding others soon:
There are many different estimates for the size of ancient Rome. The majority of the figures I have seen, estimate somewhere between 750,000 to 1.2 million citizens by 200 AD! Quite a place if the entire world population at the time was only ~ 240 to 410 million souls.