In 1990, a sculpture known as Kryptos was installed right outside CIA headquarters in Langley, Virginia — and it was inscribed with four encoded messages. While the first three codes were all solved within a few years, the final message has remained shrouded in mystery to this day.

Three of the four coded messages in artist Jim Sanborn’s Kryptos sculpture, famously placed at CIA headquarters in 1990, have been solved. Now, the solution to the fourth code, K4, will be going up for auction.

In 1990, Sanborn’s sculpture was installed in the courtyard of CIA headquarters in Langley, Virginia. Ever since, countless people have tried to solve the codes carved into its surface, though the secret behind the fourth code has never been uncovered.

But when Sanborn sells the answer to K4, just

See Full Page