@hannie.rb/TikTokA student and TikToker at Northern Arizona University, Hannie (@hannie.rb), discovered a tunnel beneath the campus.

While walking on campus at night, a student at Northern Arizona University made a strange discovery: they stumbled upon a hidden tunnel beneath the feet of students.

In the TikTok video, the astrogeology student Hannie, who currently has over 5.6 million views, notices a small gap beneath the sidewalk. Upon closer inspection, they see that there is a hole within this gap — and through this hole, a brightly lit tunnel becomes visible.

“I know you saw this,” they say, bringing the camera as close to the hole as possible. Although no one enters the frame throughout the video, it is clear that the tunnel is actively being used.

While many viewers encouraged Hannie to report it to the police, they shared a follow-up video stating that this “maintenance tunnel” was built during their time at the university. They also explained that they reported this hole to the school administration because it could be a “safety issue.”

However, Flagstaff, where Northern Arizona University is located, has a long and eerie history regarding mysterious tunnels.

A Tour Under Flagstaff

According to the Northern Arizona University student publication The Lumberjack, there have long been legends about the tunnels beneath the school and Flagstaff in general.

Some of these legends are difficult to verify. For instance, the commonly accepted legend states that some tunnels were built in the 19th century by Chinese residents who were blamed for a devastating fire in 1886 as an escape route. However, there is limited concrete evidence for this claim.

@hannie.rb/TikTokA screenshot from Hannie's video showing a small point of light shining from beneath the sidewalk at Northern Arizona University.

However, the other uses of these passages are well documented. Historically, the tunnels beneath Flagstaff have been used for both legitimate and nefarious purposes. For example, some businesses have dug underground tunnels between buildings to transport goods during bad weather. To give a more criminal example, the tunnels were a favorite hiding and escape route for gamblers fleeing from police raids.

Nowadays, most of these historical passages have been closed off. The tunnels that still exist — and those recently constructed — largely serve a practical purpose. According to the university, most of these tunnels support the institution's hot water infrastructure.

Of course, Flagstaff is just one of countless cities throughout history that have utilized tunnels for various purposes.

A Brief History of Secret Tunnels

Finding the oldest example of the concept of a “secret tunnel” requires being quite strict in the definition of “tunnel.”

ValerioMei/Adobe StockWater Aqueduct Park in Rome.

Under a broad definition, the oldest “tunnel” can likely be traced back to the development of water systems in the ancient world. Roman aqueducts and the ancient Persians' qanāt systems are among the earliest examples of tunnel-based water infrastructure, ultimately leading to the creation of drainage and sewage tunnels necessary for public health.

There are also a few early examples when it comes to hidden corridors that people could travel through.

gilitukha/Adobe StockThe entirely underground ancient city of Derinkuyu.

For example, the ancient city of Derinkuyu, located in modern-day Turkey, was entirely built underground. Initially thought to have been excavated as a storage area, it has housed over 20,000 residents over time, according to the BBC. This would typically occur during times when the local population was hiding from invaders.

Today, modern tunnels largely serve practical purposes and can be found in the most unexpected places. As shown in Hannie's video, if you look closely enough, you will start to see them around you.