Eight genuine puzzles from the ancient world, from undeciphered scripts such as Linear A and the Indus script to Stonehenge, the Nazca Lines and the Sea Peoples: what we know and what remains open.
Plenty of "ancient mysteries" online have been solved, or were never mysteries at all. But some genuine puzzles remain. These eight are taken seriously by historians and archaeologists, and each one is the subject of ongoing research.
1. Linear A
The Minoans of Bronze Age Crete wrote in a script known as Linear A. A later script, Linear B, used by Mycenaean Greeks, was deciphered in 1952 by Michael Ventris and turned out to be an early form of Greek. Many Linear B signs resemble Linear A, so we can roughly sound out Linear A words, but the language itself remains unknown.
2. The Indus script
The Indus Valley Civilisation left thousands of short inscriptions, mostly on seals. The texts are very short, there's no bilingual inscription like the Rosetta Stone, and the language is unknown. Some scholars even debate whether it fully represents language. It remains undeciphered.
3. Rongorongo
On Rapa Nui (Easter Island), a set of wooden tablets carries glyphs called rongorongo. Only a couple of dozen objects survive. Whether it's true writing, when it developed, and whether contact with Europeans influenced it are all debated. It hasn't been deciphered.
4. The Phaistos Disc
Found in 1908 in a Minoan palace on Crete, this clay disc is covered in stamped symbols arranged in a spiral. It's unique: no other text uses the same signs. Without more examples, decipherment may be impossible. Some scholars have even questioned its authenticity, though most accept it as genuine.
5. How, and why, Stonehenge was built
We know a great deal about Stonehenge. It was built in stages from around 3000 BC, and its smaller bluestones came from the Preseli Hills in west Wales, about 140 miles away. Research published in 2024 suggested that the Altar Stone came from north-east Scotland, even further away. How people moved the stones, and exactly what the monument meant to them, are still debated. It aligns with the midsummer sunrise and midwinter sunset, and was used for burials.
6. The Nazca Lines
In the desert of southern Peru, the Nazca culture created huge figures and lines on the ground, roughly 2,000 years ago, by removing reddish surface stones to reveal paler ground beneath. How they made them is fairly well understood. Why is less clear: theories include ritual paths, links to water and fertility, and astronomy. Researchers using drones and AI have found hundreds of previously unknown figures in recent years.
7. Who were the Sea Peoples?
Around 1200 to 1150 BC, many Bronze Age societies in the eastern Mediterranean collapsed. Egyptian records describe attacks by groups modern historians call the Sea Peoples. Who they were, where they came from, and whether they caused the collapse or were refugees from it, remain open questions. Most historians now see a combination of drought, earthquakes, trade breakdown and conflict.
8. The Etruscan language
The Etruscans dominated much of Italy before Rome. Their alphabet came from Greek, so we can read Etruscan inscriptions aloud, and we know many words. But the language isn't related to most others in Europe, and with few long texts, much of it is still not fully understood.
Be wary of "mysteries" that aren't
Claims that ancient monuments needed lost technology or outside help usually ignore the skill and organisation of the people who built them. The real puzzles are about evidence that hasn't survived, and that's why new discoveries keep changing the picture.
Sources and further reading
- English Heritage: Stonehenge
- Nature: Altar Stone origin (2024)
- Wikipedia: Linear A
- Wikipedia: Indus script
- Wikipedia: Late Bronze Age collapse
- UNESCO: Lines and Geoglyphs of Nasca
Facts checked on 20 October 2026. Spotted an error? Tell us and we will correct it.
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Chris is a freelance writer and editor covering a wide range of topics with a focus on accuracy and depth.
Last updated: 2026-04-25 · Fact-checked by editorial team