Tokyo Subway System (Tokyo, Japan) 5

Hands down the best subway system I have ever seen. There are three
overlapping lines (or maybe four?) - one government run, and two private
ones. The central Tokyo line is called the JR Yaminote line, and this
one loops through many of Tokyo's can't miss neighborhoods like Shibuya,
Shinjuku, Harajuko, Ikebekuro, Tokyo Station, and Roppongi.

The trains are clean, modern and absolutely continuous, I don't think I
ever waited more than three minutes for a train. The AC cranked in
every train I was on, and go into the basement of any commercial
building in Tokyo, and you are likely to run into a subway system. The
Japanese clearly know how to move massive numbers of people
efficiciently.

Sometimes the trains got a little crowded, but hey, it's Tokyo - the
planet's highest density of humans.

The one thing you need to look out for is if you reach some of the
lesser traveled stations, you won't always find English translations of
the stops.