Donald Trump has, once again, been proven wrong.

Back in September, POTUS traveled to Otay Mesa, California, to show off a section of the U.S.-Mexico border wall that he claimed was "virtually impenetrable." Trump toured the area with reporters, Army Corps engineers, and border protection officials in tow, bragging about the ways no one could get through or over the newly constructed wall replacement—not even professional climbers.

"We have, I guess you could say, world-class mountain climbers. We got climbers," Trump said at the time. "We had 20 mountain climbers. That's all they do—they love to climb mountains ... Me? I don’t want to climb mountains. But they are very good, and some of them were champions. And we gave them different prototypes of walls, and this was the one that was hardest to climb ... This wall can't be climbed."

Rick Weber, a retired engineer who co-founded the Muir Valley rock climbing park in Rogers, Kentucky, took Trump's claims as a challenge: "You don’t tell a bona fide rock climber something’s impossible to climb," he told TIME.

Weber has constructed a wooden replica of Trump's Otay Mesa-area border wall, and has invite climbers to attempt to scale it during this weekend's "Rocktoberfest" rock climbing festival at Red River Gorge. Weber will also hold a competition to see who can climb the 18-feet-high structure the fastest. 

TIME reports the replica has already been climbed by several people, including 8-year-old Lucy Hanock. 

Per the publication: 

Hancock didn’t use any ropes or other tools to climb the wall, but wore a belay, a safety device designed to catch a falling climber. An adult climber, Erik Kloeker, was up and over the wall in about 40 seconds.

Lucy called the climb "easy."

Last week, Weber shared a blog post announcing the competition as well as addressing Trump's statements about the replacement border wall in question. The 75-year-old specifically expressed doubt over the president's claims that 20 accomplished mountain climbers had failed to scale the wall. 

"No one in our climbing community knows any of these 20 mountaineers," he wrote. "I doubt if they exist."