DENVER (KDVR) — The monolith trend appears to be making a comeback. Another version of the mysterious, mirrored pillar popped up without warning in northern Colorado. Its origins are unknown.

A Reddit user posted in the Fort Collins subreddit over the weekend saying they went to the structure near Bellvue. In the thread, Redditors speculate on the monolith’s origin, but the details haven’t been confirmed.

This is not the first time a mysterious and mirrored monolith has popped up. The phenomenon that started in 2020 reappeared this month.

A somewhat similar structure was found north of the Las Vegas Valley over the weekend of June 15 and 16, according to Nexstar’s KLAS.

The Las Vegas Metropolitan Police Department took it down a few days later on June 21.

No confirmed connections have been made between the monolith in northern Colorado and the one near Las Vegas.

Back in 2020 several monoliths were found across the world after one appeared at random in a rural part of Utah. They started to pop up without warning in California, New Mexico and around the world, then would disappear just as quickly.

Where the monoliths come from and what they mean hasn’t been publicly explained. Their remote locations have made it even harder at times to figure out how they were installed, or how long they were there before anyone noticed.

Vox reports the slabs are 10 to 12 feet tall. Many speculate they’re a reference to the science fiction movie “2001: A Space Odyssey.”

Only one of the monoliths, the one installed in Atascadero, California, in late 2020 has a known backstory. Locals told the Atascadero News they were inspired by the Utah monolith, and director Stanley Kubrick’s classic movie, so they sought to recreate the phenomenon locally as a form of guerrilla art.

It is worth noting that the structure found in Colorado is rectangular, as opposed to the triangular shape seen in both the Las Vegas monolith and many of the 2020 monoliths.