Disguised as a charming three-story home in the heart of Brooklyn, 58 Joralemon Street is passed by hundreds of people every day, completely unaware that it’s actually a front for a secret subway ventilation shaft. This building is just one of many ‘fake buildings’ scattered throughout New York City.

An urban explorer recently took a tour of these hidden structures and shared the footage online, where it quickly went viral, gaining over 563,000 views in just a few days. Like 58 Joralemon Street, many of these fake buildings hide essential equipment needed to keep the city running smoothly. With so much going on in New York City, sometimes fake buildings are necessary to discreetly maintain its infrastructure. However, the purpose of some fake buildings has been a mystery for decades, leading to all sorts of conspiracy theories, from secret spy bases to government labs conducting experiments or even housing aliens.

One of the most famous examples is 33 Thomas Street—a huge, windowless skyscraper originally built by AT&T as a telephone switch center. Since AT&T stopped using it in the late ’90s, nobody knows for sure what goes on behind its concrete walls, leading to plenty of speculation. Some rumors suggest it’s a storage site for emergency supplies, while others claim it’s a surveillance site for the National Security Agency.

Exploring the hidden fake buildings of NYC would be an awesome way to discover the city and learn about its secrets. It’s a unique adventure that reveals how much goes on behind the scenes in this bustling metropolis.