New York Penn Station
Concourse level of Penn Station, New York. That grain in the photo is not accidental — it is quite dim inside the station. In a great architectural travesty, the old station was knocked down in the 1960s to build Madison Square Garden. The loss of Penn Station energized opposition to modernization-at-all-costs, and indirectly led to the preservation of many other historically significant buildings in New York City and elsewhere.
With basketball games going on above it, the station is almost entirely underground. The tracks are below the concourse, with a maze of escalators to confuse newbies. It's like an airport concourse, but without even a view of the outdoors.