NOVA scienceNOW: Kryptos

The most enigmatic of all codes in the most clandestine of all places has yet to be fully broken. “Kryptos,” a coded sculpture in the courtyard of CIA headquarters in Langley, Virginia, contains a long string of seemingly nonsensical letters that conceal a message devised by sculptor James Sanborn. Some portions have been deciphered, but the last bit remains a mystery.