Mumbai, India, commonly ranks among the most densely populated cities in the world. Hindustan Times/ via Getty Images

Jakarta, Indonesia, was named the most populous city in the world in the United Nations' World Urbanization Prospects report last year.

But population doesn't directly translate into how crowded the cities actually are — the 42 million residents of the Jakarta metro area, for instance, are spread over more than 2,500 square miles.

Residents of other cities, like Dhaka, Bangladesh, and Mumbai, India, have a bit less room, making them some of the most densely populated cities in the world.

Rankings of the most densely populated cities vary across different sources due to different population frameworks. Some sources limit their estimates to city limits, while others include the entire population of a greater metro area.

The UN's World Urbanization Prospects report, however, highlights a broader societal move to city living.…