Which cities have an underground rail system?

Question

Just doing a bit of idle research; Obviously, there's London, and I'm aware of New York and the Paris Metro, but I was wondering how many other cities there are. Any you could name would be helpful.

Nb: I'm looking solely for mass transit systems that go underground, vs. things like the Metrolink in St Louis or an above-ground monorail system.

Answer 1

Here's a full list:  http://en.wikipedia.org/wiki/List_of_rap...

Answer 2

Philadelphia (both trains and trolley cars), Chicago, and Camden, New Jersey

Answer 3

Berlin, Hamburg, Cologne, Frankfurt, Munich, Barcelona, Madrid, Bilbao, Valencia, Alicante, Tokyo, Moscow, Ciudad de Mexico etc etc

Answer 4

Tokyo, Osaka.

Singapore

A lot of major cities in the US.

Vienna

Barcelona

Madrid

Answer 5

Here's two:  Washington DC's is almost entirely underground, and Chicago's is partially underground.

Answer 6

Also, some PATH (Port Authority TransHudson rapid subway) goes underground as well except for west of Grove Street.