11. Sao Paolo, Brazil

"What building did you say they lived in?" Finding it in the largest mass of condensed apartment buildings anywhere would be like finding a needle in a haystack. Sao Paolo has a population of over 18 million people! While the buildings are not super tall (with only a single structure at over 200 meters tall) this skyline is nevertheless stacked. Sao Paolo has a fleet of over 500 helicopters, the second largest helicopter fleet in the world.

Metro/Urban Population: 18.3 million