There’s one problem with this fact though. While the residential population of Manhattan (1.7 million) and the size (22.82 square miles) would mean that only 28K people would fit in one square kilometer, according to https://wagner.nyu.edu/files/rudincenter/dynamic_pop_manhattan.pdf, about 4 million workers stay at the city during a weekday, declining to about 2 million at night. That’s still more then the residential population. This also means that over 65K people are in one square kilometer (that’s way more then Rome’s suspected population density of 40-50K) and over 170K per square mile (bigger then the 70K said). Plus, Midtown and Lower Manhattan are full of skyscrapers were people work meaning that the density is higher then the few tens of thousand that live in both districts (Possibly over 700K in Midtown alone!). So, in reality, Manhattan is most likely even more dense then Ancient Rome!
