5 THINGS ABOUT MYSTERY MONOLITHS.

Shiny metallic monoliths have been cropping up in surprising spots around the world and no one knows why.

1 LIKE KUBRICK'S CLASSIC, WITH FEWER APES

The first appeared in the Utah desert about two weeks ago. It disappeared after generating much excitement internationally among science-fiction fans, harkening to Stanley Kubrick's 1968 film, 2001: A Space Odyssey. In the Kubrick movie, an alien monolith is a recurring symbol that appears to play a role in the development of human evolution.

2 ROMANIAN MONOLITH A SURPRISE

Another appeared just a few days later in rural Romania, but vanished on Tuesday. The 2.8-metre monolith, which appeared to be covered in circles, was just a stone's throw from the Petrodava Dacian Fortress, built between 82BC and AD106.

3 `IT WAS THERE — NOW IT'S DISAPPEARED'

Andrei Carabele, the mayor of the Romanian town of Piatra Neamt, told residents there was “no reason to panic” when the object first appeared. He joked that he was honoured “teenage aliens had chosen our city” to plant the symbol but it would have been better if they had obtained a building permit first. Carabele had hoped the hilltop structure would become a new tourist attraction, but when he went to visit it again it was gone. “On Sunday afternoon it was there — and now it's disappeared.”

4 MADE BY A `BAD LOCAL WELDER'

The local newspaper, Ziar Piatra Neamt, said “a bad local welder, made it ... now all that remains is just a small hole covered by rocky soil.” The sheet metal structure had a badly-welded joint.

5 CARTED OFF IN A WHEELBARROW

Utah's monolith also came to an ignoble end, according to The New York Times. A photographer who claimed to have witnessed the structure being destroyed said it took about 15 minutes for two men to tear it down, break it apart and cart it off in a wheelbarrow.