From castles, cathedrals, and palaces to miles-long bridges, golden temples, and sky-scraping glass towers, the world is full of magnificent feats of architectural engineering. While the purpose of most of these structures is known, there are still plenty of human-made monuments that boggle the minds of even the most acclaimed scientists and archaeologists. Here are 11 such monuments that remain a mystery.
Original photo by Stephanie LeBlanc/ Unsplash
Carnac Stones (France)
The Carnac Stones are a group of more than 3,000 megalithic standing stones in the French village of Carnac, Brittany. These stones date back to the Neolithic period and were probably erected between 3300 and 4500 BCE. They are one of the world’s largest collections of menhirs — upright stones arranged by humans. There is no real evidence to confirm their purpose, but that hasn’t stopped researchers from hazarding guesses. Some theorize they were used as calendars and observatories by farmers and priests. According to Christian mythology, the stones are pagan soldiers who were petrified by Pope Cornelius. Local folklore, meanwhile, says that the stones stand in straight lines because they were once part of a Roman army. The story goes on to say that the Arthurian wizard Merlin turned the Romans to stone.
Easter Island Moai (Chile)
Over 2,000 miles off the coast of Chile, Easter Island (Isla de Pascua) is the one-time home of a Polynesian people called the Rapa Nui. Scattered across the island are around 1,000 moai, giant hand-carved stone statues of human-like figures that are half-buried in the earth. The Rapa Nui landed on the island sometime between 700 and 800 CE, and are believed to have started making the moai around 1100 CE. Each moai weighs 14 tons and stands 13 feet tall on average, so it’s hard to imagine how they were transported and hauled into place. One theory is that the islanders used a system of ropes and tree trunks. Their purpose has also been the subject of much debate. To the Rapa Nui, the statues may have stored sacred spirits.
Nazca Lines (Peru)
Southern Peru’s Nazca Desert is covered with hundreds of geometric designs. These ancient geoglyphs range from simple shapes to plants and animals such as a hummingbird, monkey, llama, and whale. The Nazca Lines date back to around 200 to 700 CE, when the Nazca people who lived in the region created them. Researchers have struggled to agree upon the purpose of these giant works of art, particularly since they are best seen from the surrounding hills and by plane. Among many theories are astronomical maps, indicators of sacred routes, and water troughs. An alternative take is that they were created to be observed by deities from the sky.
Stone Spheres (Costa Rica)
In Costa Rica’s Diquis Delta is a group of around 300 polished stone spheres, some just a few inches in diameter and others measuring up to seven feet and weighing 16 tons. Employees of the United Fruit Company stumbled across the spheres in the 1930s while clearing a jungle to build a banana plantation. Scientists have so far been unable to pinpoint an exact date of their origin, instead suggesting that they appeared sometime between 200 BCE and the 16th century CE. They are commonly attributed to the Diquis people, yet their purpose is a mystery. They might have been property markers of ancient chiefs, and some even think they may be remnants of the lost city of Atlantis. Some of the spheres were even detonated in the hope of finding gold inside.
Temple of Bacchus (Lebanon)
The Baalbek temple complex in northeast Lebanon is one of the most intriguing Roman ruins on the planet. Its centerpiece is the well-preserved and monumental Temple of Bacchus. The age of the temple is unknown, although it was most likely erected in the second century CE. Most historians agree that emperor Antoninus Pius commissioned it in honor of Bacchus, the god of wine and intoxication. What has been baffling archaeologists ever since the temple’s rediscovery in the late 19th century is how the Romans succeeded in building it. It is staggering to think that humans without heavy machinery could hoist the 42 Corinthian columns (19 of which remain standing) of the colonnade, since each stands 62 feet tall and 7.5 feet in diameter.
Hagar Qim (Malta)
Located on the Mediterranean island of Malta, the UNESCO World Heritage Site of Hagar Qim is one of seven prehistoric temples in Malta and is believed to date to between 3800 BCE and 2200 BCE. The site’s name translates to “standing stones,” and one of the largest weighs in at more than 20 tons, measuring nearly 23 feet in height. The site was first excavated in 1839 and consists of a series of rooms lined by these megaliths. Parts of the chamber align with the sunrise and sunset of the summer solstice. This and the other temples on the island all appear to have been built in the same period, which has left archaeologists puzzled — there is little evidence of any civilization capable of such building feats on the islands at that time.
Göbekli Tepe (Turkey)
Could a set of ruins in southeastern Turkey be remnants of the world’s first temple? That’s one of the key questions archaeologists ponder as they explore Göbleki Tepe, a series of huge stone pillars that are some 6,000 years older than Stonehenge. Now a UNESCO World Heritage Site, the landmark was ignored for centuries, dismissed as little more than a cemetery. In the mid-1990s, excavations began and experts soon realized it was a treasure trove of history. The pillars weigh as much as 10 tons each and create massive stone circles. Radar surveys of the area indicate a number of additional circles are still buried underground. Göbleki Tepe is older than writing and older than agriculture. But who were the Neolithic people who built this, and how and why did they do it?
Yonaguni Monument (Japan)
Experts are divided as to whether the underwater rocks near Japan’s Yonaguni Island are a human-made structure or naturally occurring. In the 1980s, divers discovered what appears to be a rectangular monument, measuring 165 feet long and 65 feet wide. Some scholars believe that it is the remains of a pyramid, perhaps from a long-lost submerged city belonging to an ancient civilization. Meanwhile, others insist the rocks have been shaped by millennia of the ocean’s currents. Similarly, while some argue that markings on the rock’s surface are proof of ancient human involvement, others say they are simply scratches. For the time being, the Japanese government seems to agree with the latter and does not recognize the Yonaguni Monument as culturally significant.
Great Zimbabwe Ruins (Zimbabwe)
The Great Zimbabwe Ruins are the largest ruins in sub-Saharan Africa. This medieval city was once a trading hub and possibly the capital of the Queen of Sheba’s realm. The remains consist of the Great Enclosure (perhaps a royal residence), the Hill Complex (possibly the religious heart of the city), and the Valley Ruins (houses which suggest the city once had a population of 20,000 people). In total, the Great Zimbabwe Ruins extend across an area of 200 acres. The city is thought to have been abandoned in the 15th century, for reasons scientists aren’t sure of.
The Maya people of what is now Mexico were incredibly advanced when it came to writing, building, and knowledge of astronomy. Yet scientists still know little about other parts of their culture. By the time Spanish conquistadors arrived from Europe, the Maya civilization had already fallen, and historians still debate the cause. Some of the finest Maya ruins are at Palenque, in the Mexican state of Chiapas, an elaborate complex that includes a palace and several temples. Thought to have been constructed between 500 and 700 CE, it features plaster carvings and decorations that are still remarkably well-preserved. The city at Palenque is a marvel of design but remains shrouded in mystery since we may never know why it was abandoned around 900 CE.
No list of mysterious sites would be complete without the Neolithic monument at Stonehenge, which is known worldwide and continues to mystify visitors. The enormous stones are estimated to have been placed between 2500 BCE and 2200 BCE. Hundreds of even older burial mounds have also been uncovered in the surrounding area. Some of the stones come from several hundred miles away in Wales, leading archaeologists to speculate how they were transported. Others are from nearer parts of Wiltshire. What was Stonehenge’s purpose? Many believe it was a spiritual site, and people still flock to it as the sun rises on the summer solstice, when sunlight rises above the Heel stone at Stonehenge and falls directly onto the middle of the circle.
The moon has long captured our imaginations. It’s embedded deep in mythology around the world, and even became the first calendar for many ancient people. But our connection to the moon goes even deeper — its symbiotic relationship with the planet Earth is unique within the solar system, and without it, we might not even exist. These 10 facts about our nearest lunar neighbor just might deepen your appreciation for Earth’s one and only natural satellite.
The Moon Is Bigger Than Pluto
If you were in grade school before 2006, when the International Astronomical Union reclassified Pluto, you may still think of it as a full-fledged planet. While the classification isn’t, technically, entirely about size, it’s hard to overstate just how itty-bitty Pluto is. Its radius is only about 715 miles, compared to a mean radius for the moon of about 1,080 miles.
Some other moons even outrank full-fledged planets, size-wise. Our solar system’s two largest moons, Jupiter’s Ganymede and Saturn’s Titan, are both larger than Mercury!
The Moon Is 27% the Size of Earth
While Earth’s moon is only the fifth-largest moon in the solar system, everything changes when we grade on a curve: At more than a quarter the size of Earth, our moon is, by far, the biggest when compared to its planet. According to NASA, if the Earth were a nickel, the moon would be the size of a coffee bean.
This gives our moon an outsize influence on our planet compared to others, in ways that almost seem magic — but are very much real.
The Moon Causes the Tides to Change
Not only does the moon influence the tides, but we wouldn’t even have tides without the moon. Its gravitational pull tugs up the water on the sides of the Earth facing and opposite the moon. This action is called tidal force. The moon’s gravity also affects land, but not nearly as much as water.
Forces besides the moon influence tidal patterns, too. Since the Earth isn’t entirely covered in water, land masses can affect how dramatic the tides get. The sun can have its own effects on tides, too, although it’s not as noticeable until the sun, moon, and Earth line up for a new moon or a full moon, causing tides to get much bigger.
The Moon Helps Stabilize Earth
The moon’s unique relationship with the Earth, it turns out, is crucial for preventing and slowing major, deadly climate shifts — at least the naturally occurring ones. The moon’s large mass helps keep Earth from tilting too quickly, preventing the kind of wobbles that created dramatic climate conditions on Mars. It could be that larger moons are one of the factors a planet needs to create and sustain life.
The “Moon Is Made of Cheese” Myth Is a Millenia-Old Joke
Today, the idea of the moon being made of cheese is a deeply -embedded fanciful trope appearing in everything from children’s books to B-movies to tasty snacks. It’s central to the premise of the Wallace and Gromit cartoon “A Grand Day Out.” But where did this cutesy reference to the moon’s appearance come from?
There’s no evidence of a widespread historical belief that the moon was actually made of cheese. Its origins lie in various folktales passed down in many cultures’ oral traditions. In some, a fox tricks a wolf into believing the reflection of the moon in a well is cheese, which convinces him to dive in. In others, it’s a human simpleton who dives into the well. The Aarne-Thompson Index, a folktale classification system, even has specific listings for “the Wolf Dives Into the Water to Eat Reflected Cheese” (34) and “Diving for Cheese” (1336). Variations of these myths appear all over the world, from the Zulu Kingdom to the Scottish Highlands. Typically, the person or creature thinking the moon is cheese is the butt of the joke.
“The Moon Is Made of Green Cheese” (referring to the freshness of the cheese, not its color) evolved into a figure of speech describing an easily duped person (think “I have a bridge to sell you”) as early as 1546, when it appeared in a proverb by English writer John Heywood. The trope remained incredibly common for centuries to come.
The term has also been used as a variation of “when pigs fly,” as in German playwright Bertolt Brecht’s play Good Person of Szechwan.
The Moon Is Deeply Scarred From Asteroids and Comets
Celestial bodies crash into the moon all the time, creating its somewhat chaotic surface. Often, these meteors are the size of a speck of dust, but larger collisions are not uncommon. During the 2019 total supermoon eclipse, casual observers and professionals alike caught the tiny flash of a meteoric impact, which caused an explosion roughly equivalent to 1.7 tons of TNT.
Debris that size hits the moon roughly once a week, and NASA’s Lunar Resistance Orbiter has tracked more than two dozen new impact craters since 2009. The lunar proximity to Earth means the same stuff that’s hitting the moon is whizzing past us, too — but without an atmosphere, the moon is much more vulnerable.
Of course, the bigger scars are from bigger impacts, and we’re still seeing some of those today. In 2014, Spanish astronomers observed an 800-pound meteorite crash into the moon’s surface. Researchers with the Southwest Research Institute, University of Toronto, and University of Southampton were able to date some of the moon’s larger craters in 2019, and later created a one-minute visualization of their research with music that corresponds to each impact.
12 People Have Walked on the Moon
The most famous moonwalkers are probably the first two, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin, who made their historic mission in 1969. But that was just the first of many crewed lunar landings in the Apollo program over a three-year period. All together, 12 people have walked on the moon so far. But nobody has set foot there since Apollo 17 in 1972 — and so far, only American white men have had the opportunity.
Another 12 astronauts reached the moon without walking on it, including the crews of Apollo 8 and Apollo 10, which orbited the moon without landing. Others were on later missions, but had different tasks, like Michael Collins, who stayed in orbit 60 miles above the moon during Apollo 11, making sure they could all get home safely, while Armstrong and Aldrin went to the surface.
Scientists Think a Collision of Two Planets Created the Earth and Moon
While there are many theories regarding its origins, the most widely accepted one is that the moon arose after a protoplanet approximately the size of modern Mars crashed into the Earth about 4.5 billion years ago, knocking loose debris from both bodies that would gradually become the moon. New research (as of 2021) proposes that there were actually two impacts: one extremely fast one that knocked the material away, and another slower one that helped merge the debris.
The Moon Is Darker-Looking on the Earth Side
You’ve heard the phrase “the dark side of the moon,” referring to the side that’s not facing Earth. Technically, the sun shines on both sides of the moon — but the majority of those dark, mottled patches — actually expanses of solidified lava called lunar seas, or maria — are on the near side. At more than 1,600 miles wide, Oceanus Procellarum, or Ocean of Storms, on the western edge of the near moon, is the largest of them all.
These vast plains of basalt come from volcanic activity, but the exact mechanism of their formation is still being studied. Some were created or at least helped along by asteroid impacts, but that’s not the whole story either, since similar hits typically don’t get the same reaction on the far side.
This isn’t to say that the far side is pristine. It’s heavily pockmarked with impact craters.
The Man in the Moon Comes From Lunar Seas
There are many lunar seas smaller than the Ocean of Storms, and several of these, along with brighter lunar highlands, make up the face that some people in the Northern Hemisphere see on the surface of the full moon.
Your mileage may vary depending on where you live and how your brain sees things, but usually the Mare Serenitatis (Sea of Serenity) is one of the eyes. The other eye is formed by the Mare Imbrium, or Sea of Showers, immediately to the west.
The nose, appropriately, is not a mare, but a sinus, or bay: Sinus Aestuum, or Bay of Seething. The mouth, which is open to interpretation but sometimes described as “grinning,” is a combination of Mare Nubium (Sea of Clouds) and Mare Cognitum (Sea That Has Become Known). In the Southern Hemisphere, the moon is flipped vertically, and many people see the Northern Hemisphere “face” as a rabbit. But some see a more joyful little face, too: Mare Frigoris, or Sea of Cold, could be seen as a much more defined grin.