65-year-old artist Jim Sanborn created the cypher sculpture Kryptos 20 years ago, and still, professional cryptologists and code cracker hobbyists have not cracked the last part of the 1,800 letter code, poked through a large block of petrified wood. The artist promised to leak an important clue to the New York Times shortly.

The sculpture is currently roosting outside the CIA headquarters in Langley, Virginia, mocking them mysteriously. It says something about something invisible and important hidden somewhere. Find out what before it’s lost forever. “I don’t have that many decades… left in me,” Sanborn said.