Here's a great graphic from LSE Cities that depicts population density in a much more granular and telling way than a simple summary statistic like people per square mile could:
One thing to note here is that while it's tempting to interpret the tall bars as indicating tall buildings, that's not necessarily the case. The densest areas of New York and Hong Kong really do feature enormous towers, but Mumbai is dense largely because the average household occupies very few square feet of building footprint.
