TIL that beneath Grand Central Terminal in NYC lies a massive hidden basement called M42, which was once a WWII target. It remained secret for decades and is large enough to fit two football fields, housing key equipment for powering the terminal.

https://en.wikipedia.org/wiki/M42_(sub-basement)
#til #todayilearned
https://www.reddit.com/r/todayilearned/comments/1g4odm6/til_that_beneath_grand_central_terminal_in_nyc/