On November 3, 1990, CIA authorities revealed a new sculpture outside of the Agency's cafeteria. The mysterious sculpture was named Kryptos (an ancient Greek word for "secret" or "hidden"), and it was created by Jim Sanborn, an American sculptor whose works mainly focus on topics such as magnetism, secret messages, and mysteries of atomic reactions.

For years, this 12 feet high piece of art has been a real challenge for many cryptographers from around the globe, whose skills in solving cryptographic puzzles apparently weren't enough to fully solve Sanborn's enigmatic artwork.

The main structure is made out of four massive copper plates and it contains four encrypted messages, only one of which remains unsolved and continues to stump experts to this day. According to Sanborn himself, deciphering the encrypted message will be something akin to a treasure hunt. After nearly three decades of unsuccessful attempts to solve the riddle by numerous experienced code-breakers, the fourth part, which is composed of only 97 letters, is still a mystery.