One of the things we learned on the Untapped Cities tour of the Secrets of Grand Central was that there are walkways in the massive windows of the terminal! This photo was shot by Mandeep Bedi of Taste Architecture on the tour. If you look closely, you’ll see someone crossing right between the first zero in 100. The walkways connect the offices above Grand Central so the employees don’t have to walk through the busy terminal, according to Untapped Cities tour guide Tamara Agins.
According to Jim Cameron, former NBC News anchor and director,
They’re accessible (though public access is seriously discouraged). Just go to the entrance to Michael Jordan’s Steakhouse on the mezzanine level near Vanderbilt Ave. and take the elevator up two or three floors. When you get off, go left and through the un-marked door on your left. Walk out and you’ll have a panoramic view of the station from almost roof-level.