Some interesting city population trivia for those pub quizzes.
| 1 | Tokyo | 35,197,000 |
| 2 | Seoul | 22,770,000 |
| 3 | Mexico City | 19,411,000 |
| 4 | New York | 18,747,320 |
| 5 | São Paulo | 18,333,000 |
| 6 | Mumbai | 18,196,000 |
| 7 | Delhi | 15,048,000 |
| 8 | Shanghai | 14,503,000 |
| 9 | Calcutta | 14,277,000 |
| 10 | Moscow | 13,750,000 |
I had a list from the WHO but then I found what looks like a more detailed list on Wikipedia so this top ten data comes from there.