Mass transit...Subways...A rapid transit, underground, subway, elevated, or metro(politan) system is a railway—usually in an urban area—with a high capacity and frequency of service, and grade separation from other traffic. In most parts of the world these systems are known as a "metro." In Buenos Aires the network is called Subte, while in most of North America and in Glasgow, Scotland, United Kingdom it is a "subway".

Of course we are often shown TV/movie scenes in New York where it's referred to as the subway. If you're a ER fan, you know in Chicago it's referred to as the el or L. Our closest, Atlanta has the Marta. When I was in Rome and Paris it was always called the Metro....then London, although officially it's the underground, I heard it mostly call the tube.

When I went to New York in January the loft I stayed in had a huge framed print (like 5ft x 7ft) of the subway map, which was very helpful in planning the daily excursions. So I did a little searching when I came home and found a poster for myself---London too.