Nearly four million people ride the Cairo Metro each day, a network stretching out over 69.8km of track and servicing 57 stations.

BBC: Subway systems by the numbers

The Cairo Metro is much larger than the Algiers Metro, which consists of one line, carrying around 300, 000 riders each day to just 10 stations via 9.2km of track.

BBC: Subway systems by the numbers

It may be difficult to believe, but in all of Africa, only two cities have subway systems: Algiers, which just launched its metro at the end of 2011, and Cairo, where the subway has been around since 1987.

BBC: Subway systems by the numbers