Archaeology is meant to help us understand our past. But sometimes it throws up objects that are so unusual, so advanced or so baffling that we can’t be sure what they really are or what they were used for. From astronomical devices as complex as any modern machine to children’s toys that suggest the ancient Egyptians knew how to fly, these intriguing objects pose more questions than they answer.

Read on to discover the most mysterious historic artefacts archaeologists are yet to decode...

How could a man-made tool associated with modern times end up encased in rock dating from the Lower Cretaceous period? That's the question that's baffled scientists since the so-called ‘London Hammer’ was unearthed in London, Texas in 1936. It was discovered by local man Max Hahn, who noticed wood protruding from the rock and cracked it open to expose the hammerhead and ignite a furious debate. If it was truly from the Cretaceous period then man was still another 100 million years of evolution away from creating such a tool. The hammer is currently displayed in the Creation Evidence Museum of Texas.

When Austen Henry Layard unearthed an 8th-century-BC piece of rock crystal at the Assyrian palace of Nimrud in Iraq in 1850, he assumed that it had been used as a magnifying glass or a burning glass that concentrated sunlight to start fires. Others dismissed it as a piece of decorative inlay. Italian scientist Giovanni Pettinato, from the University of Rome, had another theory: that it was a lens from a telescope instrumental to the Assyrians' deep knowledge of astronomy. It became known as the Nimrud Lens, and although other experts say the optical quality of the lens isn’t good enough to be of use, the name stuck.

At first glance, this 4th-century Roman glass cup decorated with scenes of the death of King Lycurgus is pretty typical of its time. But if you light the cup from different angles, something magical happens: it turns red when lit from behind and green when lit from the front. Researchers discovered that the effect was created by suspending gold and silver nanoparticles in glass – a previously-unknown process they hope can be used in modern optics, microscopy and nanotechnology as well as in the arts.

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The Voynich Manuscript is an illustrated codex handwritten by an unknown author in an unknown script known as 'Voynichese'. It's been carbon-dated to the early 15th century and its style is reminiscent of the Italian Renaissance. Over the years, many people have tried to read the manuscript and failed, including legendary code-breaker Alan Turing. The latest theory, posited by historian Nicholas Gibbs, is that it's a women’s health manual, based on the large number of images of women bathing. Fundamentally, the manuscript's meaning is no clearer today than it was when it was rediscovered in 1912.

Ever since it was restored from a pile of 123 broken pieces found in a storeroom in the Museum of Ontario Archaeology, the so-called ‘Holey Jar’ has only grown more mysterious. Its provenance is the first issue. The storeroom contained items bequeathed by Welsh archaeologist William Francis Grimes from an excavation of the Mithraeum – a Roman temple in London dedicated to Mithra – as well as items from archaeologist Leonard Woolley from his excavations in the ancient Mesopotamian city of Ur. More perplexing still is the purpose of its titular holes. The jar is the only known artefact of its kind and its exact function remains a mystery.

Did the ancient Egyptians know how to fly? A small wooden bird discovered in a tomb in Saqqara raised the prospect that they might have understood the principles of aviation long before they were thought to be first discovered. Made in 200 BC and measuring five-and-a-half inches (14cm), with a wingspan of seven inches (18 cm), it certainly looks like a toy glider. However, when glider designer and manufacturer Martin Gregorie constructed a replica it was too unstable to fly. Consensus among experts is that it was a ritual object or toy, or perhaps a weather vane to be placed on sacred boats to indicate the direction of the wind.

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Is it a child’s toy? A weapon? Or just something that looked cool on an ancient Roman bookcase? These small hollow objects, made of copper alloy with 12 flat pentagonal faces, have been perplexing archaeologists and historians since the first example was unearthed in England in 1739. Since then, 116 individual dodecahedrons have been found right across the former Roman Empire, from Hungary to Belgium, often alongside hoards of coins. Some observers have theorised that they were fortune-telling devices or knitting spools for making gloves.

When this astoundingly complex machine was found on an ancient Greek shipwreck off the tiny island of Antikythera in 1900, it looked like an unremarkable lump of green metal. A few months later it split open to reveal tiny gears, triggering more than a century of speculation. Some claimed it was an astrolabe for tracking the stars, others that it was a navigation device. In 1905, German philologist Albert Rehm proposed that it was an astronomical calculating machine that could predict eclipses decades in advance. Modern research has confirmed one thing for sure: its level of sophistication was quite extraordinary for its time.

An ancient shrine discovered in 2019 in Berenike, an old port city on the Red Sea in Egypt, has left archaeologists perplexed. The 1,700-year-old 'falcon shrine' features the remains of 15 headless falcons, an iron harpoon and a stone monument depicting two unknown gods. Burying falcons for religious purposes was not unknown during the period, but they were rarely decapitated. And the pillar found in the room with a Greek inscription reading "it is improper to boil a head in here" has really confounded archaeologists.

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The Shroud of Turin is a burial cloth that bears a faint, yellowed image of a naked, crucified man. Some Christians believe it is the burial cloth of Jesus of Nazareth and make pilgrimages to the Cathedral of St John the Baptist in Turin, Italy, where it has lived for more than four centuries. The cloth has sparked debate among historians and theologians: some believe it is real, others that it is a medieval hoax. Modern science has completed hundreds of thousands of hours of intense study and research on the shroud, and doubts over its authenticity remain.

What was a terracotta Roman head doing buried in Mexico? That was the question archaeologist Romeo H Hristov asked himself in 1933 when he uncovered this intriguing artefact in a grave in the Toluca Valley, just 43 miles (69km) from Mexico City. Was it evidence for transatlantic contact between the Romans and Mesoamericans? Was it brought to the continent by Spanish conquistadors? Or was it no more than a hoax? We may never know the truth, but recent tests dated the figurine to sometime between the 9th and 13th centuries AD, rather than the 2nd century AD first put forward by Hristov.

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In 1872, workers digging a hole for a fence post near the shoreline of Lake Winnipesaukee in New Hampshire unearthed a mysterious egg-shaped object, six feet (1.8m) underground. When they wiped away the mud, they discovered the quartzite egg was covered with carvings, including an ear of corn, mysterious circles and, most bizarrely, a face. One hundred and fifty years later we still don’t know for sure who made it or why. At the time, the American Naturalist journal described it as "a remarkable Indian relic", suggesting it was made to commemorate a peace treaty between two tribes. Others have suggested that it's a birthstone or some kind of ancient tool.

In 1974, a wedge-shaped object was discovered buried alongside a pair of mastodon bones in Aiud, Romania. The items were found 35 feet (11m) underground and the mystery deepened when it emerged that the wedge was made of aluminium. The presence of the mastodon bones suggested the wedge was around 11,000 years old, but smelting aluminium only started in 1856. A mystery for the ages? Perhaps not. The current thinking is that the wedge is simply a tooth from a modern-day excavator bucket.

This 500-year-old geographical map currently on display in the Topkapi Palace Museum in Istanbul accurately depicts several places that had not yet been discovered when it was written. Created by Piri Reis, an Ottoman admiral and cartographer, the map outlines the coasts of Europe, Africa, South America and the Caribbean. Perhaps based on a lost map by Christopher Columbus, it includes Nova Scotia, the Andes and a southern landmass once thought to represent Antarctica. No one is quite sure exactly how Piri got hold of his information.

Long associated with Aztec and Mayan cultures, crystal human skulls, carved from clear or milky-white quartz, have long caught peoples’ imaginations. Their smooth, flawless surfaces suggest something almost otherworldly, and New Age figures attributed them all kinds of paranormal abilities. Sadly, nearly all the crystal skulls on display in museums are fakes. The British Museum's skull first appeared in Eugene Boban's curiosity shop in Paris in 1881, but was denounced as a fake by a Mexican curator when Boban tried to sell it in Mexico City in 1885.

Read on for more ancient mysteries we still don’t know the answer to