Two decades ago, the CIA commissioned a sculpture to grace one of the courtyards at its headquarters in Langley, Va. The sculptor who won the commission, Jim Sanborn, designed a curving copper wall with a secret code embedded across four panels.
Code-breakers eventually cracked the first three, but the fourth panel continues to stump even the pros at the CIA and the National Security Agency.
So now, for the first time in 20 years, Sanborn is dangling a new clue to the mystery. He joins All Things Considered guest host Mary Louise Kelly to talk about the clue, which first appeared in Sunday's New York Times.