Above, from a 2012 issue of The Defenders: Dr. Strange, the Black Cat, and the Silver Surfer in what is obviously the abandoned City Hall Station on the IRT. Here’s the station as it looked when construction was almost complete:
Note that there’s only one track because this was the southern terminal station and it was a loop. Downtown trains ran around the circle and headed back uptown.
So far, so good, but there’s a note at the bottom of the page:
And that’s wrong. Beach built an experimental pneumatic subway under Broadway in 1870, with a line that ran about a block and a half. It was interesting but impractical and was permanently closed in 1873. The IRT subway’s City Hall station is a few yards east of that closed-off tunnel and the line did not run under Broadway, so the construction of the IRT in 1900-1904 did not hit the old tunnel.
When the BMT subway was extended south from Canal Street, under Broadway, in the late 1910s, excavation for the new City Hall Station uncovered the Beach tunnel and enveloped it: construction of the new station destroyed all the remnants of the abandoned one. There’s a plaque in the station that mentions it. The IRT City Hall Station was abandoned for passenger use in 1945, although trains still run through the loop to turn around.
So Marvel’s writer got it wrong: there are two abandoned City Hall stations: the Beach station, which has been demolished, and the IRT station, which is the one they used for the background. I don’t know if it’s still true, but fifty years ago Marvel Comics would send you a “no-prize” if you pointed out a mistake like this. The prize was literally an empty envelope.