On Thursday, 11Alive’s investigators made a stunning find just yards away from where a piece of I-85 collapsed – an elaborate, and illegal, skate park built right under the interstate, cemented around its pillars.

After we discovered the almost 30-foot wide, sloping cement park, the Georgia Department of Transportation told 11Alive that the park was never permitted. A spokesperson for the agency said crews would begin dismantling the park soon.

PREVIOUS | A secret skate park was built under Interstate 85, just yards from the collapse

But, how did it go unnoticed for so long?

During a Tuesday GDOT press conference, Commissioner Russell McMurry said that crews “immediately did an inventory of our existing locations, and it's safe to say there are no other bridges with this material under it in Georgia."

But while there may be no more of that particular flammable material under Georgia’s bridges, 11Alive investigators found a disturbing amount of other potentially flammable materials close to the site of the collapse, including pallets of concrete mix sitting under tarps, stacks of plywood lying about and other construction materials. All appear to have been used to create the skate park in under the roadway, which was last inspected in 2015.

PHOTOS | Hidden skate park under I-85

One skater, Andrew Rodriguez, told 11Alive people have been using the secret skate park for months and have never been challenged. He was hanging out there Thursday.

"There hasn't been too much paying attention, but who's going to be patrolling miles and miles of overpass," he asked.

But while GDOT officials may not have know about the illegal construction, many of the young people 11Alive spoke to at the Old Fourth Ward Skate Park in Atlanta did. They call it “bridge life,” and it’s like a secret skateboarding society where young people hang out – under bridges or freeway overpasses.

"It’s the best thing in the city so far," 29-year-old Major told 11Alive. He declined giving his last name because he knows the people involved in constructing the illegal skate park found under the I-85 bridge.

"You just take, like, unused spaces and put some cement there, and all of a sudden, it's a cool place to go to," he told 11Alive’s Ron Jones.

Skaters who spoke to 11Alive said it was supposed to be a secret, but that secret was exposed and when someone sent our station photos of the park under the Interstate, just yards away from where I-85 collapsed during last week’s massive fire.

11Alive investigator Andy Pierrotti saw first-hand the elaborate and sophisticated construction. Major told 11Alive those involved know their craft.

"They just truck it (cement) in a flatbed truck and drop it off, mix it there and build it," he said.

Major told 11Alive that most of the activity goes on between 3 a.m. and 7 a.m., so that the construction goes unnoticed and stays undercover. When asked whether there are more skate parks like this one out there:  "Ah dude! Probably a hundred,” he claimed. “Yeah, I think a hundred for sure."

At this time, 11Alive has not found any proof of them. Even so, 11Alive asked exactly how those skateboarding enthusiasts would find these parks. Major just said slyly, “That's part of the fun. You don't know. You got to go look for them."

PHOTOS | Under the bridge aftermath