In the ongoing battle to protect the city's subways from acts of terrorism, the NYPD always needs to stay one step ahead of the terrorists. As the police adapt to the terrorists' methods, the terrorists adapt to the police's adaptations, and the cat-and-mouse game goes on. But the NYPD has one secret weapon on its side: a fake house. You see, among the lovely three-story brownstones in Brooklyn is one extra-special home, one that really isn't a home at all. It's merely a façade that serves to disguise a passage into the dark subway tunnel. And nobody knows where it is except for the NYPD and maybe some people in the MTA!
The NYPD allowed the AP to visit the hidden exit — fronted by the phony house in a quiet residential neighborhood — on the condition that its origins and location not be disclosed. The department also barred photos.
Located in the tunnel just east of the river, the exit leads to a grimy lit set of metal stairs that ascend past utility boxes and ventilation shafts into a bleak, windowless room with a door. Anyone opening the door would find themselves on a stoop — part of the facade replicating a town house.
The passageway once was secured from the outside only by a giant bolt in the middle of the door that was opened with a tire iron. It's now rigged with silent alarms and motion detectors that would alert police to an intruder.
The security reflects concerns that a terrorist could use the passageway to sneak into the system, or try to tamper with the ventilation to make a chemical or biological attack more lethal.
On second thought, we don't really get what the point of this secret exit is, exactly. As the last paragraph suggests, it actually seems to be kind of a security liability, and we're not sure what the benefits are. Nevertheless, it's still pretty cool, in a real-life spy movie sort of way, which is probably why they built it.