Japan's capital city Tokyo has the busiest metro system in the world, followed by Moscow and Shanghai, according to figures from Union Internationale des Transports Publics (UITP), a nonprofit organization that promotes public transport worldwide.

UITP collected data on the world's metro systems based on a series of key indicators including ridership, number of lines, network length, numbers of stations and fleet size.

Asia is home to seven of the top 10 busiest metros, according to the report. Four cities from China made this year's top 10, with Shanghai ranked in third place, followed by Beijing in fourth place, Guangzhou in eighth place and Hong Kong in 10th place.

Let's take a look at the 10 busiest metros in the world.