10. Osaka is home to some 19.2 million people.

9. Beijing is one of the oldest cities in the world.

8. Mumbai is built on seven islands and is also home to the Indian film industry (Bollywood.

7. Dhaka is the centre of Bengali culture.

6. Cairo is best known as the home of one of the ancient wonders of the world; the ancient Egyptian Giza pyramid complex.

5. Mexico City sits high on the plateau known as the Valley of Mexico, 2,240m above sea level.

4. São Paulo is a city of huge contrast, a place where extreme poverty meets great wealth.

3. Shanghai used to be a small fishing village.

2. Delhi has been in existence for over 2,000 years.

1. Tokyo is the largest city on Earth, with a population of 37.4 million people.