The case of the mysterious monoliths: Here's where curious structures have appeared around the world

So many metal pillars have mysteriously appeared and disappeared over the past few weeks that the world, collectively, has struggled to keep count.

However, one thing is for sure – this is starting to look like an international stunt. While no one has yet claimed ownership of the monolithic structures (apart from one), many social media users have suggested they are the work of artists.

Here is a timeline that breaks down what has happened since the appearance of the first monolith in Utah last month.

The first monolith was discovered in Utah on November 18.

Once news broke about the appearance of the first monolith in Utah, people started to flock to the site. Less than 10 days later, the silver pillar was removed. The incident was recorded by photographer Ross Bernards, who was at the site on November 27 when four men arrived and dismantled the structure.

A second monolith was discovered in Romania on November 27

This monolith appeared on Batca Doamnei Hill, in the city of Piatra Neamt. The monolith later disappeared on Tuesday, December 1.

Though it bore a resemblance to the Utah monolith, it didn't appear to be the same structure, with the Romanian version displaying etchings on its exterior.

A third monolith was discovered in California at Pine Mountain on Wednesday, December 2

The first one to appear in California was atop Pine Mountain, and this is the only one whose creators have come forward. A few days after its appearance, it was destroyed by several men who live-streamed themselves tearing down the shiny three-sided structure and leaving a cross in its place.

Now, a group of artists have come forward claiming to be behind the monolith and have replaced it with a new one.

Metal artists Wade McKenzie, Travis Kenney, Randall Kenney and Jared Riddle have said they are the creators of the California monolith, in a YouTube video posted on Monday, December 7. The four men and a group of local friends and fabricators placed their stainless steel obelisk back on Pine Mountain just before midnight on Saturday, December 5, the video stated.

During this time, a monolith in Pennsylvania appeared, but this one was placed outside a store by the business's owner.

Another monolith was discovered in southern California, this time in the Los Padres National Forest, on Saturday, December 5

San Luis Obispo resident Matt Carver was camping with friends at a site near Arroyo Grande when they came across the gleaming gargantuan structure while shooting drone footage, reported the Los Angeles Times.

Over that weekend, four more monoliths were discovered in Colombia, Germany, Spain and Belgium

A golden structure was found on Saturday, December 5 in Chia, Colombia, in what looks like an open field.

Other monoliths also appeared in a small German town, at a church ruin in a village in Spain and in a potato field in Belgium.

On Sunday, December 6, three further monoliths were discovered in California, on the Isle of Wight and in the Netherlands

In California, the structure appeared off a trail at a Canyon Country park, local news sites reported, but it was removed the following morning.

In England, witness Tom Dunford told Sky News that he was walking with his fiancee and sister on Compton Beach on Sunday, December 6, when they came across the silver metal structure.

In the Netherlands, hikers found the object on private land near the Kiekenberg nature reserve in northern Friesland province, a spokesman for the Dutch Forestry Commission said.

"We know that it was probably placed this weekend because some hikers who were walking there found it, but we don't know how it got there," forestry commission spokesman Imke Boerma told AFP.