It’s been years since a network of secret tunnels was discovered beneath Tampa, but their purpose still remains a mystery.

The subterranean passageways below Ybor City may have been used to smuggle immigrants, alcohol or even money for the Mafia, experts theorized.

“These are quite substantial,” Dr. Lori Collins with the University of South Florida’s Center for Digital Heritage told News 6.

“I mean, you can stand up and maybe bend over a little bit, depending on how tall you are. But you can certainly travel through them.”

Everything about the tunnels — an estimated two or three in total — remains a mystery that officials are still working to unravel today.

One of the last known access points into the tunnel burned down in 2001, but the city was dumbfounded to uncover another in 2018 during a construction project near an old bottling factory.

Taking advantage of the entryway, researchers dove into the network to try and map out the expansive system — even finding a spring inside.

“When we went into the one tunnel — all the way to the back end of it — we knew that there had been mapped an artesian well nearby,” Collins told the outlet. “And we did find where it was bubbling up inside the actual tunnel space today.”

They also discovered a trove of bottles, which researchers say could prove that the tunnels were used to smuggle alcohol during Prohibition — a reasonable theory considering the city was once infamously run by the mafia.

Another theory is that the tunnels were used to safely transport money in a time when the city was “lawless,” Rodney Kite-Powell with the Tampa Bay History Center told the outlet.

The now-burned-down tunnel once connected the Ybor Cigar Factory, for which the city was named.

One less exciting theory is that the tunnel is nothing more than a rudimentary sewer system.

“They likely were originally built as sewer tunnels, the first kind of proper sewer system, and they’re a little bit smaller,” Kite-Powell explained.

“And then the one that I’ve actually been in: that curious system was abandoned in the late 1900s or so, maybe 1920s.”

Researchers made 3D renderings of the tunnels, but still don’t know the full length — though some theorize it runs the 3 miles to the Port of Tampa.