Several hundred slabs carrying the same strange message are pressed into the roads of two continents. The method is understood. The hand behind it is not.

The Inca ran an empire of millions without writing a single letter. They used knotted cords instead. We cracked the numbers a century ago, and everything else on those cords has resisted us ever since.

Ricky McCormick was found in a Missouri cornfield in 1999 with two folded sheets of capital letters and numbers in his trousers. Twenty-seven years later, the FBI's cryptanalysts and thousands of volunteers still cannot read a single line.

For seventy years we have been able to say the syllables of Minoan prayers and account books out loud. We still have no idea what a single word of them means.

A three-metre slab covered in an unknown script stood at the mouth of the Singapore River for centuries. In 1843 an engineer blew it up to widen the harbour. One fragment survives, and the writing has never been deciphered.

A civilization of a million people left behind planned cities, covered drains, standard weights and about four thousand tiny inscriptions. After a century of work nobody can read one, and some scholars argue it was never writing at all.

A Hungarian count gave away his library in 1838. Inside it sat a small, fat book written in a script that matches no alphabet on earth. Nearly two centuries and a dozen rival decipherments later, not one sentence of it has been read in a way other scholars accept.

A serial killer taunted San Francisco with encrypted letters. Two of his four ciphers have been cracked — one took 51 years — yet his identity remains a blank.

A 15th-century codex filled with impossible plants, bathing women and a script no one has ever decoded has defeated medieval scholars, WWII codebreakers and modern artificial intelligence alike.

For 35 years, 97 letters on a copper sculpture at CIA headquarters have defeated the world's best codebreakers. In November 2025 the answer was sold for $962,500 — to an anonymous buyer sworn to keep it secret. The mystery was sold. It was not solved.

In 1908, a clay disc stamped with 241 mysterious signs emerged from a Minoan palace on Crete. It may be the world's first printed text — and no one can read it.

Easter Island's wooden tablets carry one of the last undeciphered scripts on Earth — and a 2024 dating study hints it may have been invented with no outside help at all.