The Statue That Stumped the CIA

In 1990, artist Jim Sanborn installed a giant, S-shaped copper scroll in the courtyard of CIA headquarters in Langley, Virginia. Named Kryptos, the curvy sculpture is covered in thousands of punched-out letters. It looks like a beautiful piece of art, but it’s actually a massive puzzle designed to tease the world's greatest spies.

The left side hides four secret messages. Codebreakers cracked the first three, known as K1, K2, and K3. Two use a Vigenère cipher, where a secret keyword changes how every single letter shifts in the alphabet. The third uses a transposition cipher, which scrambles perfectly good letters into a confusing grid.

But the final message, a 97-character section called K4, has completely stumped everyone for decades. Even the professional analysts working inside the CIA building can't figure it out. It is one of the most famous unsolved ciphers on the planet.

Sanborn wants K4 solved, so he occasionally drops hints. He revealed that certain chunks of letters translate to words like "BERLIN" and "CLOCK." But knowing a few answers isn't enough. Until someone discovers the hidden math connecting the scrambled letters to the real words, K4 remains totally unbroken.