There are some downright bizarre happenings around the world right now that you probably don't even know about, but you should. Some can be explained — even though it might have taken a long time (sometimes even centuries) to explain them — while others are so mysterious that even the best historians, archaeologists, and scientists in the world haven't been able to quite figure them out. The colossal rocks that form England's Stonehenge, for example, have been sitting in that field for eons now and still, nobody can ration how, exactly, they got there when the people of that era didn't even know what the wheel was because it hadn't been invented yet.

Newer discoveries such as the largest known dinosaur footprint on the earth, the remains of the real Mona Lisa, and a peculiar fruitcake that's been frozen in Antarctica for hundreds of years, have offered up easier explanations to researchers. But whether or not we know the whos, whys, and hows behind these findings, we should still know about them, nonetheless. So, here are 10 discoveries from around the world that scientists haven't been able to explain yet, and 10 that are so obvious even we could have worked them out.

20 Inexplainable: Diquis Spheres In Costa Rica

Some of the most mysterious discoveries in history have been uncovered slowly, over time, since the 1930s, in the Diquis Delta of Costa Rica. More than 300 strange stone spheres have been found in this Central American nation, ranging from just a few centimeters wide to weighing more than 16 tons, and neither scientists nor archaeologists can figure out how or why they were ever created in the first place. They do agree, however, that these artifacts were handmade by people who lived between 700 C.E. and 1530 C.E., Atlas Obscura says, and they were likely carved out of larger boulders into their perfectly spherical shape by old-fashioned pecking and grinding methods.

19 Inexplainable: The Antikythera Mechanism

Did you know that the ancient Greeks had computers, too? Well, sort of. They had the Antikythera mechanism, which was an early version of an analog computer that they used to predict astronomical events. According to Mental Floss, the first of these artifacts was first found in 1900 in a sunken Roman ship that was believed to have sailed during the 1st century BCE. It wasn't until the '70s, however, that scientists started recognizing its worth and trying to figure out how the complex mechanism works. The Antikythera mechanism features bronze pieces, gears with triangular teeth, and rings that all interconnect in order to — we think — predict the future. But still, no one can figure out who used the object and to what end.

18 Inexplainable: Fairy Namibian Circles

 

There's something downright strange going on in the Namib Desert in Southern Africa: the landscape is covered in perfectly circular patches where the grass — or any plant life, for that matter — simply refuses to grow. What might be even weirder is that these barren rings, ranging from 2 to 15 meters in diameter, are often encircled by a halo of healthy, lush grass? While the official term for it is actually arid grass formation, the mysterious patches have been nicknamed fairy circles for their enchanted aesthetic. These are nature's crop circles, and scientists can't seem to figure them out.

17 Inexplainable: The Lost City Of Atlantis

Whether the island of Atlantis is real or simply a work of fiction nobody knows. The History Channel calls Atlantis "a likely mythical nation," but many historians think it was actually once a real place. Plato wrote about the powerful kingdom that existed there in his dialogues "Timaeus" and "Critias," saying that the island sank into the ocean around 9,600 B.C. Some people have linked The Lost City of Atlantis to a rather popular tourist destination, actually — the Greek island of Santorini — because it was once destroyed by a volcanic eruption. However, the story still just doesn't add up.

16 Inexplainable: Earthquake Lights

It's lightning! It's a UFO! No, it's earthquake lights! These rare flashes illuminate the night sky when there is no storm stirring and sometimes not even a cloud overhead. Earthquake lights can take on many different shapes and colors, from floating blue orbs to a quick green bolt. Unlike lightning, these lights come from the ground rather than the sky and they typically take place before an earthquake. This was the case before the 2009 L'Aquila, Italy, quake; the one in Quebec in 1988; and dozens of other devastating tremors. They don't always occur, but when they do, they usually predict a looming natural disaster. Scientists, however, still don't quite know what causes the mysterious flashes.

15 Inexplainable: The Shroud Of Turin

Could the Shroud of Turin be Jesus' burial cloth? Some say maybe. The famous shroud is a centuries-old linen cloth that depicts an image of a crucified man. While the original sepia-colored image of the face might look a bit questionable to some, the black-and-white negative of it undoubtedly shows a striking resemblance to Jesus Christ, and in 1958, the late Pope Pius XII agreed. The only question is whether the linen is actually real or the work of a really good artist, and that is still being debated. In the meantime, the Shroud of Turin is being held at the Cathedral of Saint John the Baptist in Turin, Italy.

14 Inexplainable: The Hobbits Of Flores

When the 18,000-year old remains of the Flores man (who was actually a woman) were discovered on the Indonesian island of Flores in 2003, researchers thought they once belonged to a human, just like the rest of us, only really small. The skull they excavated was less than a third of the size of ours, Smithsonian Magazine says. Later developments revealed that the bones belonged not to a homo sapien, but a homo floresiensis, a different species of archaic human that existed after the Neanderthals went extinct. Because of her elfin size, they nicknamed the primal woman "Hobbit" after J.R.R. Tolkien's Lord of the Rings. However, many skeptics question how a hominoid with a brain of that size could possibly develop the sophisticated tools they found nearby.

13 Inexplainable: Stonehenge

Just looking at the colossal stacked stone planks that make up Stonehenge is just about enough to make your back hurt. Now think about how people in prehistoric times moved these boulders over hundreds of miles even prior to the invention of the wheel. This historic site in Wiltshire, England, remains one of the world's greatest mysteries today. The rocks that make up this ring of stones weigh about 25 tons each and stand around 13 feet high. The people of the late Neolithic period started erecting these grand structures around 3100 B.C.

12 Inexplainable: Naga Fireballs

Imagine the shock the first person who watched a mysterious glowing ball rise from Thailand's Mekong River felt; or rather, the horror. Over the years, thousands of these eerie orbs have been spotted rising over the 300-mile-long stretch of water in this remote part of Asia. Reports say they float up to 600 feet then disappear. Superstitious locals think the burning red lights come from the mouth of the giant sea serpent living in the Mekong, Naga, which is how the fireballs got their name. Scientists, however, theorize that they're caused by deposits in the water that decompose and turn into methane gas, whose bubbles rise to the surface of the river and ignite when they meet oxygen at the top.

11 Inexplainable: The Marfa Lights

The Naga fireball theory could almost be applied to the Marfa Lights in Texas, even though there isn't nearly as much water in the desert as there is in the Mekong. Reports say these orbs are about the size of basketballs and vary in color. They've been known to twinkle, dart, hover, and even split into two. The first mention of the Marfa Lights was in 1883 when a farmer who saw them while herding his cattle thought they were Native American campfires, but no ashes were found. Like the Naga fireballs, scientists say the Marfa Lights could be caused by gases that rise from desert swamps.

10 Obvious: Underwater Monolith In The Mediterranean

In 2015, researchers discovered a 39-foot monolith on the seafloor off the coast of Sicily. When divers then went down to examine the peculiar stone statue, an array of holes that had been drilled into the monolith suggested that it was actually manmade. It also didn't match the other rocks on the seabed that surrounded it; rather, the particle of rock they tested turned out to be 40,000 years old, from the last ice age, when that sliver of land that's now 130 feet under water was dry. It's clear, then, that the people who lived on these islands during the late Pleistocene period erected the newly discovered underwater pillar.

9 Obvious: Mona Lisa's Remains

After much deliberation by art detectives and historians alike, it seems that the 500-year-old remains that were excavated from Florence, Italy, once belonged to Leonardo da Vinci's muse. According to the Independent, Lisa Gherardini del Giocondo, who died in 1542 at the age of 63, is the woman in da Vinci's most famous piece, the Mona Lisa. She was allegedly married to a rich silk merchant and became a nun after her husband died. Although the woman's skull was not found with her remains — meaning that researchers aren't yet able to digitally reconstruct her face to be sure — the odds, they say, are overwhelmingly high.

8 Obvious: World's Largest Dinosaur Footprint

There's no mistaking the enormous, 1.7-meter crater that was recently found in Western Australia: it's undoubtedly a dinosaur footprint. Scientists are in agreement that the several indentations that were discovered on the remote northwestern coast of Australia — dips that are so big that most humans could lie down in them — were made by a very large member of the sauropod family (such as a brontosaurus) about 130 million years ago. In fact, there are about 21 different types of dino tracks represented in this region and they're among the largest in the world.

7 Obvious: Declaration Of Independence Copy

A parchment copy of the Declaration of Independence was recently uncovered with a distinctly different feature than the original. The 56 signatures at the bottom were in a different order — not grouped by state but rather mixed together — but why? That's the question that could have left many perplexed but didn't end up stumping too many history buffs. Clearly, the copy of the document was commissioned by someone who supported "strong national government and identity," The History Channel says, and wanted to highlight the group as a unified whole as opposed to members of their separate, respective states.

6 Obvious: Viking Women Were Warriors

In 1948, women officially and permanently gained the right to join the United States Army, but there were obviously female soldiers long before then. In fact, just last year, the DNA of excavated Viking warrior remains to date back to the 10th century revealed that this warrior was a woman. With her in her grave were a selection of weapons and two horses, which suggests she was one of high rank as well. While some researchers might have been startled by the discovery that this Viking soldier was a lady who stood only 5 feet and 6 inches tall, we can't say we're all that surprised.

5 Obvious: Potential Life In Space

Even the late Stephen Hawking said he was "more convinced than ever that we are not alone." Most scientists are in agreement that another life is indeed present somewhere in the universe, which is why they work so hard to find it. Thus, whenever news breaks of a new development pointing to the possibility of aliens, it doesn't actually cause that big of a stir. For instance, in 2016, scientists discovered a planet orbiting Proxima Centauri, the nearest star to Earth's sun, in its habitable zone (meaning: it could have water. Also meaning: it could have life). But did you hear about it? No.

4 Obvious: Centuries-Old Fruitcake In Antarctica

Recently, several artifacts were discovered in Cape Adare, Antarctica, from the Terra Nova Expedition led by Robert Falcon Scott between the years of 1910 and 1913. Among the relics was a fruitcake so fresh that the scientists who found it said it looked and even smelled "almost edible," according to the Antarctic Heritage Trust. The fact that a freshly baked cake was found in one of the most remote, uninhabited place on earth would inevitably sound strange to most, but further examination revealed that this particular brand of cake, Huntley & Palmers, was actually a favorite of the late explorer's. Thus, the cake was apparently left there by him, and its freshness preserved by the continent's frigid temps.

3 Obvious: The Door To Hell In Turkmenistan

In the central Asian country of Turkmenistan, there's 230-foot-wide crater in the middle of the desert that's been on fire for more than 40 years. They call it the Door to Hell because some people actually believe that the fiery hole is a gate to the underworld. And while we admit it does look quite scary, there's a perfectly reasonable scientific explanation behind it. The official name of the pit is the Darvaza Gas Crater and it was created in 1971 by Soviet scientists who were drilling for natural gas reserves. When their rig collapsed, the Soviets set fire to the crater to prevent the spread of poisonous gas and it's been ablaze ever since.

2 Obvious: Yellowstone's Old Faithful

Watching Yellowstone National Park's Old Faithful geyser shoot water more than 100 feet into the sky from a hole in the ground is a rather wild sight. The geothermal feature shows just how alive the earth is, constantly brewing inside. The geyser erupts at regular intervals — on average, every 78 minutes, according to Popular Science — due to a process of magma forming and heating rock, which then heats water to a temperature that makes it shoot up through a narrow opening and into the sky, wowing Yellowstone visitors time after time.

1 Obvious: The Sixth Great Extinction

One of the most alarming discoveries of our time — but one that is simultaneously the most undeniably true — is the fact that humankind is currently amidst the sixth great extinction in history. Just last year, researchers said that the next mass "biological annihilation" was already underway, according to The Guardian, and we are living in it. Billions of species have been lost due to the overpopulation of humans and overconsumption, and while we can all take steps to halt the downward spiral, it looks like Earth will not be able to sustain life for much longer. Historically, mass extinctions have taken place about every 100 million years, and the last one was 65 million years ago.