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 2025, the answer was sold — to a buyer sworn to silence.

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.

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.

An 1885 pamphlet claimed a fortune in gold lies buried in Virginia, its location locked in unsolved ciphers. Skeptics say the treasure never existed — yet people are still digging.

In 1897, Edward Elgar slipped a note of curling symbols to a young friend. She never managed to read it — and neither has anyone else since.

For over 250 years, a short row of letters carved on an English garden monument has defied every attempt at decipherment — reportedly including Darwin and Dickens, and certainly the codebreakers of Bletchley Park.

In January 2012 an anonymous image on 4chan promised to find "highly intelligent individuals." Three global puzzle hunts later, a runic book remains unread — and nobody knows who was asking.