Kryptos sculpture outside CIA headquarters in Langley, Virginia.
Wired.com

An enigmatic Kryptos sits in front of CIA headquarters in Langley, Virginia, and, after 24 years, the work, unveiled on November 3, 1990, has yet to be decoded. The sculptor who created it, Jim Sanborn, has decided to issue the latest clue to its meaning, reports the New York Times.

Standing at 12-feet-tall and made up of copper, granite, and wood, the work has created a type of cult following among, for example, the tech nerds who read Wired.

By 1999, nine years after the work went up, fans had deciphered three of the sculpture’s four messages. The final passage—97 characters long—has proved resilient to thousands of code-breakers.

By 2010, Sanborn had grown impatient with the progress of his fans and decided to release a clue to help solve the puzzle—the 64th through 69th characters spelled “Berlin.” Although the divulging of the clue led to a “tsunami” of guesses, fans turned up empty-handed.

So to coincide with the 25th anniversary of the fall of the Berlin Wall, the artist said he thought it was worth returning to the topic. The clue he gave to the 70th and 74th position was “clock.”

“Reading” the letters from 64 to 74, therefore, produces the phrase “Berlin clock.”

What could “Berlin Clock” refer to? When asked if it was referencing a famous timepiece known as the “Berlin Clock,” the artist simply stated, “There are several really interesting clocks in Berlin.”

To devise the code, Sanborn worked with a retired chairman of the CIA’s cryptographic center, Edward M. Scheidt. When asked whether Scheidt expected people would still be banging their heads trying to decode the Kryptos, he replied, “No, not really” with a chuckle. “But the technique that I used obviously worked.”