Category talk:Railway stations located underground

What does "located underground" mean?
A bunch of stations on this list are manifestly above ground, like Grand Central Terminal, though its tracks are underground. What's the criteria for inclusion? "All tracks must be underground?" PRRfan (talk) 14:26, 16 March 2016 (UTC)
 * The criteria is that it has underground tracks, even if there are also on-ground tracks. See, for example, Porter station. עוד מישהו Od Mishehu 10:57, 15 January 2018 (UTC)