There are two levels: The upper level & The lower level
I may be wrong but I am on the impression that there are at least three levels.
Two main levels
Two main levels. The concourse level with the ticket booths and grand central market. The lower level is the dining concourse and some extra tracks. There a few ramp style corridors that give the feel of multiple levels. But it is really only two. After the east side access project is finished it will be another keve for under the dining concourse
There are at least 3 public levels. Upper Level, Concourse Level and the Lower Level.
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