As its name suggests, the subway station sits directly beneath City Hall, the oldest municipal headquarters in the United States. It's more than 200 years old.
The subway station was also beneath the City Hall Post Office and Courthouse Building, a massive French-style building that many derided as an eyesore. It was later demolished in 1939 to make way for what's today called City Hall Park.
Here's how the tracks lie in relation to the City Hall building and the adjacent park. In this diagram it's easier to see how the 6 train makes its 180-degree turnaround while allowing express trains to continue south through downtown and into Brooklyn.
From above, it's nearly impossible to tell you're above a Gilded Age architectural marvel — but a trained eye could still see some of the skylights through the overgrown gardens in the park.
Unfortunately, both entrance stairways have been sealed as well, for security reasons, so we have to head over to the in-service platforms and get on a train that can let us off in the station.
Those large gaps I mentioned earlier really are massive, and our tour guides bring over a ramp so we don't have to jump over live tracks.
Once on the platform, it really does feel like we've stepped back in time.
A hard-to-read plaque commemorates the opening of "this first municipal rapid transit railroad of the City of New York"
The station was designed by Rafael Guastavino — and it shows. The Spanish-born engineer is best-known for his arches, which can bee seen at other NYC landmarks like Grand Central Terminal and the Queensboro Bridge.
Here's a closer look at the many layers of "Guastavino tiles" that make up a classic arch.
The skylights we saw from above are still functioning today — albeit with a few less tiles.
An even more elaborate skylight provided light for the original ticket hall.
The fare gates and ticket windows are long gone, but inside this vaulted room is where passengers would have paid their nickel to ride uptown to Grand Central Terminal, Times Square, and beyond.
If you noticed some people covering their ears in the previous photo, it's because trains that pass through the station during regular service are loud. Very loud.
If this were a normal subway station, we'd be able to exit or enter through these stairways. Unfortunately all I found at the top was a padlocked door.
Overall, the station is in good shape, but it may never be returned to its former glory. Here's how it looked on a postcard at the time.
Tours aren't the only thing the Transit Museum does. It's one of the city's lesser known museums, but it has plenty of options for fans of historical transit.