It's a montage of trains and temples, skyscrapers and skateboards in this lovely video, where the flowing populations and frenetic pace of the world's ten biggest cities are set to a surprisingly soothing soundtrack.

"Biggest" needs a qualifier; these are actually the ten most populous cities on the planet. In case you're keeping track at home on where your city ranks, here's the list:

1. Tokyo, 32 million
2. Seoul, 20 million
3. Mexico City, 20 million
4. New York City, 19 million
5. Mumbai, 19 million
6. Jakarta, 18 million
7. São Paulo, 18 million
8. Delhi, 18 million
9. Osaka-Kobe-Kyoto, 17 million
10. Shanghai, 16 million

There's an interesting side note when it comes to deciding which cities made this list. The video authors note that they chose the cities according to this 2009 study by Richard Forstall, Richard Greene, and James Pick. In the study, Forstall and his team examined why the definitions of the planet's most populated cities vary so widely. They came up with a formula for defining a city in a way that they believe accurately includes its greater metropolitan area (which can often be as dense as the city itself). They start with the urban core then add surrounding communities if the following statistics are true: less than 35 percent of the workforce are engaged in farming or fishing, and 20 percent of the residents commute into the urban core for work. Which is why Osaka, Kobe and Kyoto get lumped into one big "city," which is also referred to as Keihanshin.

It will be interesting to see how these numbers change as people move and professions evolve—it's estimated that 70 percent of the world's population will be living in cities by 2050, yet the idea of "commuting" might fall to the wayside as technology allows more of us to work remotely.

[Heavy.com]