
The vast train network that criss-crosses subterranean Tokyo can be a confusing and intimidating place for the uninitiated.
Dreary, utilitarian stations drone and chime with a stream of announcements, seemingly ignored by the mass of humanity that spills onto platforms or crams improbably into carriages.
It may not be pretty, but in a city where millions of commuters travel by train daily, it boasts the precision of a finely-crafted Swiss watch, keeping Tokyo moving - even if it means pushing hundreds of people into a single carriage at rush hour.
Huge banks of computing power link 13 lines and nearly 300 stations over 195 kilometres of track, putting one train on each line every two-to-three minutes at peak times.
Video: Tokyo's vast underground rail system might not be the prettiest in the world, but it is the busiest and almost certainly the most efficient