While you'd be hard-pressed to find any American who doesn't know about the twin towers being hit by hijacked planes, the story of Tower Seven's collapse is one that a significant portion of the public is seemingly unaware of.
According to the official narrative of that day, debris that was emitted by the collapse of the North Tower started a large fire within Tower Seven – despite it never being hit by a plane.
Causing massive structural damage to the roof and middle floors, the building eventually wilted, completely collapsing at around 5.20pm, more than seven hours after the first plane hit the World Trade Center.
Given the scale of the devastation that day, and the fact that Tower Seven came down so much later in the day than the twin towers, it's understandable that news of its collapse wasn't exactly a big story in the days and weeks that followed.
However, for some, the lack of reporting on the building's collapse was suspicious. It wasn't long before some of the world's most notorious conspiracy theorists latched onto the Tower Seven collapse as evidence that the entire attack was an 'inside job'.
Indeed, the widely debunked idea that Tower Seven was brought down intentionally by controlled demolition, rather than the inferno within, remains a popular theory to this very day.
On the sub-Reddit r/conspiracy, one user posted about the notorious Tower Seven theory, pondering why nobody ever mentioned it's collapse when they were taught about 9/11 at school.
"In school, how many towers did you get told fell on 9/11?" they quizzed their fellow sceptics.
The user then wrote: "Because I was told 2. I’m 21 years old. I found out there was a 3rd one less than a year ago, and only because I was browsing a CONSPIRACY website.
"That’s messed up, I’m curious if others were also only taught about 2 towers in school or if I somehow totally forgot I was taught about a 3rd tower (unlikely)…".
The National Institute of Standards and Technology released their investigation findings into why Tower Seven fell in 2008, but this account continues to be questioned.
On Reddit, several users shared their stories of not hearing about Tower Seven until they went onto the internet in later years.
Many people on the thread refer to an infamous BBC News clip, where the graphics appear to 'predict' the Tower going down before it even happens.
This has since been explained as a simple error on the part of the production team, but that explanation seemingly isn't enough for everyone.
One user wrote: "It was also reported live on BBC that tower 7 had fallen, and it was still erect in the background of the reporter."
However, not everyone on the thread was in agreement, as another user claimed: "Tower 7 was talked about at the time, as well as the pentagon, but 7 and the pentagon took a back seat to the two big towers."
Approaching the 21st anniversary of 9/11, conspiracy theories surrounding what really happened that day show no signs of abating anytime soon.Featured Image Credit: Laperruque / Alamy Stock Photo / Shutterstock