Maybe it was once rare to stumble upon a 10-foot-tall monolith plopped in the middle of nowhere, towering in silent, vaguely alien mystery over a scenic landscape — but the curious find certainly seems to be getting rather common lately.

On Wednesday, dozens of hikers flocked to a new monolith found atop Pine Mountain in Central California. Apparently crafted from metal, the new oddity strongly recalls two other structures that suddenly appeared — and disappeared, nearly as quickly — in the Utah desert and on a Romanian plateau in the past three weeks.

There's at least one major difference about this new one, which now stands in thus far impenetrable mystery on one of the highest points in Atascadero, Calif.

"Unlike its Utah sibling, the Atascadero obelisk was not attached to the ground, and could be knocked over with a firm push," the local Atascadero News reports, estimating that, all told, the object must weigh around 200 pounds.

So that's perhaps one clue to its origins.

But for now, a solution to the broader mystery of the monoliths remains elusive. Since Utah state officials found the first structure in the state's remote Red Rock Country last month, authorities in the U.S. and Romania — where the second monolith briefly appeared — have professed amused puzzlement at their origins and whether any link exists between them.

The monoliths have each stood around 10 to 12 feet tall, with three sides and metal polished enough to reflect the sun's glare, though minor differences appear to distinguish each one from the others.

All three bear an unmistakable resemblance to the monolith famously featured in the film 2001: A Space Odyssey-- one reason, perhaps, why authorities have been so quick to blame aliens in their tongue-in-cheek responses. (The monolith in Stanley Kubrick's film had four sides.)

Andy Lewis, an adventure sportsman who lives near the site of the first monolith in Moab, Utah, says that he and a team dismantled and removed the object after dark on Nov. 27. He posted a series of images on social media earlier this week purporting to show their work in progress. A person claiming to be a witness said the monolith was removed to prevent environmental damage to the remote site from crowds of spectators.

The claim may complicate the efforts of Ripley's Believe It or Not! — which offered a $10,000 reward earlier this week for exclusive tips on tracking down the Utah monolith — and it doesn't get to the bottom of who put it there in the first place.

Nor have answers been forthcoming yet in Romania, where a reportedly shoddily crafted monolith stood for about four days outside the city of Piatra Neamt. The local police told Reuters that officers are investigating the provenance of the structure, which had been illegally placed in a protected archaeological area before its unexplained removal.

In California, meanwhile, the puzzlement has spread. In an email to the San Luis Obispo Tribune, Atascadero Land Preservation Society President Mike Orvis said he has no information to offer about the object.

"2020 continues to be an interesting year," he deadpanned.

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