New York - famed for its colossal skyscrapers and novel architecture - has hoards of striking, historical buildings and iconic neighbourhoods.
What many visitors to the city don't know, however, is that amongst the Empire State, the Flat Iron and the Chrysler Building, is a small collection of antique-style properties that don't actually function as homes or workspaces.
The exterior of these mysterious buildings blend in with the others surrounding them, but one social media star has recently made it his aim to uncover the true purposes behind these fake New York properties - honing in on five in particularly.
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One location that YouTube star Cash Jordan exposes in his latest social media upload is 58 Joralemon Street, Brooklyn Heights.
Presenting on the outside as your average townhouse - complete with a rustic, red-brick facade and three storeys - Cash explains that the building actually contains a steel girder filled with various technologies that are imperative when it comes to the function of New York City's train system.
He tells viewers: "The building was originally constructed in 1847 as a private residence, and for about 60 years, people lived here. But that all changed in 1907 when it was purchased by the Interborough Rapid Transit Company."
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The eight windows are completely blacked-out, and the door looks like it 'wasn't designed to be opened by mere mortals,' Cash adds.
The YouTuber also discovered that Strecker Memorial Laboratory on Roosevelt Island, was previously used as a laboratory during the 20th century, but is now owned by the Metropolitan Transportation Authority.
The grey brick building - complete with brown roofing and a blue door - appears like a happy home now, despite being constructed in 1892 as a lab for a nearby hospital, where 'experiments' or 'pathological and bacteriological research' were conducted.
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"Apparently it had an autopsy room, which is creepy," Cash reveals on the video, before explaining that it had been transformed it into a 'power conversion substation' for the trains.
Cash also visits Pier 34 in Manhattan - a large, brown structure on the Hudson River, which looks like an outdated factory on the outside.
He says: "You're probably wondering why there's a fake building in the middle of the river. Well the reason that it's [over the river] is because it has to be. It can't be on land because [its purpose] is under the water."
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Cash then explains that there is actually an enormous vent for the Holland Tunnell between the building's four massive walls, which connects New Jersey and New York.
"You've gotta have ventilation. 100,000 cars drive into Manhattan a day [through the Holland], and 34 million people a year make this trip, so the tunnel is a big deal."
Mulry Square in Manhattan is another fake building with an allusive purpose.
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Cash explains that the property is also owned by the MTA, and though its exact function is currently unknown, it 'relates to the healthy functioning of the subway'.
Accusing the architects of not doing a very good job disguising this particular location - being that concrete walls are completely windowless and the brick facade looks unfinished - he explains that the area in which it was built was formerly a 9/11 memorial.
"There was a lot of back and forth between local community boards, local preservation groups, and the city," he explains why the building was initially contested.
Perhaps the most eerie of them all, however, is 33 Thomas Street, which is believed to be the home of a secret National Security Agency base.
The concrete structure, first built in 1969 by AT&T, acted as 'a telephone switching center' up until the 1990s, but since has been a mystery.
The windowless building even once caught the attention of Hollywood superstar Tom Hanks, who tweeted a picture of it with the caption: "This is the scariest building I've ever seen! WTF goes on inside?"
Some conspiracy theories note that it's a headquarters for secret government experiments, others claim it's a spy base.
In 2016, however, journalists at The Intercept launched an investigation into the building, claimed to have found a series of leaked documents, indicating it was a secret hub for the NSA.
Topics: New York, Social Media, YouTube, Weird, US News