Originally Posted by Xing
It could be light rail or heavy.
Originally Posted by Crawford
You mean ANY underground rail station in ANY city?
So like Union City, NJ counts, because the light rail stations are underground?
Yeah, it is not clear what You really mean.
By subway stations do you mean any rail station, either heavy, light or commuter ubicated on an underground or subterranean level?
And what do you mean by cities, is it municipalities or metropolitan areas?
As crawford said, there is an underground light rail station in Union City that could be considered either on that city, as a separate entity or in metropolitan New York. Also PATH Have some underground and some elevated stations. If You also include commuter rail, then I think that Penn Station could be considered as such, since it is located underground, as millenium station in Chicago is.