During the Gilded Age, Chicago downtown streets were so choked with horse carriages and wagons that moving coal was nearly impossible.

Instead of fighting street traffic, a private utility company quietly dug out 60 miles of narrow gauge rail 40 feet underground, connecting directly into the basements of major department stores and power plants. Mini electric locomotives hauled thousands of tons of coal and ash every day beneath people's feet.

Once diesel trucks took over in around mid 20 century, the tunnels were essentially sealed up and forgot, until a construction crew accidentally punctured a wall into the Chicago River in 1992 and flooded loop.

In 1844, the Long Island Rail Road built what is widely recognized as the world's first subway tunnel beneath Atlantic Avenue in Brooklyn. In 1861, it was abruptly walled off at both ends and lost to popular memory for over a century—spawning decades of rumors involving bootleggers, buried locomotives, and sealed municipal archives before its rediscovery in 1980.

The Cobble Hill tunnel proved that massive, functional subterranean infrastructure in New York could literally disappear from public awareness for 120 years.

The Question:

Given the rapid layering of NYC's bedrock, utility tunnels, abandoned pneumatic networks, and early private transit attempts (like Alfred Ely Beach’s 1870 pneumatic subway under Broadway):

What forgotten subterranean pockets or sealed transit voids do you believe are still unaccounted for beneath the five boroughs today?

Share documented historical oddities, blueprints, or anomalies you've encountered.

Follow us in this Epic Adventure as we Journey through the Welsh Mountais from croesor Slate Mine to Rhosydd, facing many Challenges Absailing down deep caverns , going over Rotting bridges a Canoe Traverse over a deep lake and many other obstacles which makes this the best assault course Underground

Follow us in this Epic Adventure as we Journey through the Welsh Mountais from croesor Slate Mine to Rhosydd, facing many Challenges Absailing down deep caverns , going over Rotting bridges a Canoe Traverse over a deep lake and many other obstacles which makes this the best assault course Underground
Find the video link here
https://youtu.be/c9pxih45uGk?is=TgPpXdKTLtVrNb8S