What are monoliths? Timeline of 'mysterious' columns around the world

Few modern-day structural mysteries have garnered as much international fascination as the tall, mirrored monolith columns that have appeared in seemingly random locations since 2020.

Reminiscent of the prehistoric Stonehenge in Wiltshire, England, but rooted in Millennium-era fictional lore, monoliths are long vertical metal slabs, each approximately 10 to 12 feet tall.

Monoliths are believed to stem from Arthur C. Clarke's "Space Odyssey" series and Stanley Kubruck's 1968 famed sci-fi film "2001: A Space Odyssey," where aliens used large, black monolith-shaped machines as a guide to monitor and control humans' evolution.

However, the scores of monoliths that have appeared around the world since 2020 look slightly different from those Clarke and Kubrick imagined -- opting for a metal, often stainless steel structure.

From Utah in the United States, Wales in the United Kingdom and as far as Romania in southeastern Europe, these often unexplained structures have left officials and Internet sleuths questioning their makers and intentions.

Below is a timeline of monolith appearances internationally since 2020.

Nov. 18, 2020: Utah

The first unaccounted-for monolith appeared in Utah's remote Red Rock Country on Nov. 18, 2020, during the height of the pandemic.

The Utah Department of Public Safety Aero Bureau was working to conduct a count of big horn sheep in a portion of southeastern Utah when crew members "spotted an unusual object" and landed nearby to investigate further, according to a press release at the time.

The crew members discovered the metal monolith installed in the ground in a remote area of Red Rock, according to the release.

Just 10 days later, the monolith disappeared, with officials saying it was removed by an "unknown party."

"We have received credible reports that the illegally installed structure, referred to as the 'monolith' has been removed by an unknown party," the Utah Bureau of Land Management wrote on X on Nov. 28, 2020.

A man named Andy Lewis later took credit for the removal, sharing a YouTube video of him and a small crew detaching the monolith from the rocks.

"We removed the Utah Monolith because there are clear precedents for how we share and standardize the use of our public lands, natural wildlife, native plants, fresh water sources, and human impacts upon them," Lewis said in an interview at the time.

Despite Utah officials never specifically saying where the monolith was located, online detectives allegedly found it on satellite images dating back to 2016 and determined its GPS coordinates, according to Britain's The Independent at the time.

Nov. 27, 2020: Romania

Just as the monolith was removed from its location in Utah, another monolith was discovered across the world in Romania.

The prism was found near an archaeological site outside of the city of Piatra Neamt, on the plateau of Btca Doamnei, officials said at the time.

Piatra Neamt Mayor Andrei Carabelea took to Facebook to joke about the mysterious monolith in Romania, "My guess is that some alien, cheeky and terrible teenagers left home with their parents' UFO and started planting metal monoliths around the world. First in Utah and then at Piatra Neamt. I am honored that they chose our city," the mayor wrote.

Four days after it first appeared, the Romanian monolith disappeared as mysteriously as it arrived.

Dec. 2, 2020: California

The streak of monolith appearances continued the exact day the column was removed in Romania -- this time in California.

On Dec. 2, 2020, another monolith was discovered on Pine Mountain in Atascadero, a city in San Luis Obispo County in central California.

The 10-foot-tall and approximately 18-inch-wide monolith was found by hikers two miles up from the base of the mountain, according to local reports.

"I think it disappeared in Utah and landed right here in Atascadero," hiker Blake Kuhn told ABC News' Fresno affiliate at the time.

However, unlike the mysteries surrounding the other monoliths, the makers of the California column came forward to reveal themselves.

The four men who created and installed the third monolith are Travis Kenney, his father Randall Kenney, Wade McKenzie and Jared Riddle, they said in a statement.

"The purpose of this project was to create a positive and encouraging environment in a rather negative 2020, a year that has been plagued with health issues, political separation, and systemic racism," Riddle said in an interview with Your Tango. "This event separated all of that!"

December 2020: Various locations

After the Internet frenzy the string of back-to-back monoliths caused, several copycat monoliths started popping up around the world in Pittsburgh, Joshua Tree, Las Vegas, Boulder, Albuquerque, Russia, Colombia, Spain and more.

A Business Insider report in Dec. 2020 estimated there were 87 monolith sightings globally.

March 12, 2024: Wales

Years after the initial monolith obsession died down, the tall, mysterious structure reemerged in Wales, United Kingdom, in 2024.

The 10-foot-tall silver monolith was discovered in Hay-on-Wye in Powys, Wales, by construction worker Craig Muir while he was out for his regular hike.

Muir posted a video of the bizarre find on TikTok, saying, "I come up here most days, and I've never seen this before. Almost looks like a UFO just put it on the ground."

June 17, 2024: Las Vegas

This month, the monolith mystery continued when the Las Vegas Metropolitan Police Department took to X to share two photos of the long, vertical slab of metal they said appeared on a hiking trail near Gass Peak on the northern side of the Las Vegas area.

"We see a lot of weird things when people go hiking like not being prepared for the weather, not bringing enough water... but check this out," the department wrote alongside photos of the column.

In the photos, the tall, geometric figure reflects the rocky desert and perfectly aligns with the horizon.

A similar monolith appeared in downtown Las Vegas in December 2020, standing under the Fremont Street Experience canopy.

The monolith was removed by Las Vegas police on June 20, saying it was necessary "due to public safety and environmental concerns."