Dark secret behind completely windowless 29-storey skyscraper in New York

A man has shared the real reason that numerous US cities - including New York - have mysterious windowless skyscrapers.

The huge window-free buildings give folks a bit of an unnerved feeling and has sparked much debate about what exactly goes on inside their hidden walls.

Alien hideout? Home of a nefarious secret sect? Training school for spies?

Even Hollywood star Tom Hanks has pondered exactly what the buildings could be used for.

In a tweet back in 2017, he shared a snap of 33 Thomas Street in New York, and asked: "This is the scariest building I've ever seen! WTF goes on inside?"

But ponder no longer - because Eric Guidry, who goes by @e.guidry on TikTok, shared what the buildings were really used for. And you may be pleased - or disappointed - to know it doesn’t involve aliens.

This is the scariest building I've ever seen! WTF goes on inside?? Hanx. pic.twitter.com/nXeUI64rXm

— Tom Hanks (@tomhanks) June 2, 2017

"So that building in New York, this windowless building in San Francisco, this one in Chicago, this one in Austin and hundreds more buildings placed conspicuously across the country, in very populous locations,” Guidry says in the clip.

It turns out that the buildings are all part of AT&T's long lines network.

"Before we had digital telephony, the lines on your phones physically connected to the person on the other end's phone.

"That meant we need these massive switching hubs. Most of those buildings I showed were built in the '70s [or earlier]. "That means they didn't require actual operators.

"And because this machinery didn't particularly care if there was light or not, they just decided, why add windows?"

Giving more information on the specific AT&T building in New York featured in the original TikTok video, Eric said: "That building is 33 Thomas Street, which is known to be one of the most secure towers in the world.

"It has enough gas, water and electricity to be able to continue running independently for up to two weeks and is supposed to be able to actually withstand a nuclear blast... within reason.

"Although most of the equipment has been digitalised and you don't need it for phones, it's still critical for network and internet infrastructure.

"In fact, if you're watching this in the US, this video probably went through one of those buildings."

However, several conspiracy theorists believe that the building has been used as a National Security Agency (NAS) surveillance site.

And in 2016, non-profit organisation, The Intercept, claimed that there was 'compelling evidence', including leaked documents from NSA whistleblower Edward Snowden, that pointed towards the building having been used as a surveillance site, code-named TITANPOINTE.

According to their 2016 investigation, a former AT&T engineer said there is 'a major gateway switch' that 'routes all calls between the US and other countries around the world'.

While other theories are a bit more crazy - ranging from vampires to 'lizard headquarters'.

So who knows?