Kryptos

The most celebrated inscription at the Central Intelligence Agency's headquarters in Langley, Virginia, used to be the biblical phrase chiseled into marble in the main lobby: "And ye shall know the truth, and the truth shall make you free." But in recent years, another text has been the subject of intense scrutiny inside the Company and out: 865 characters of seeming gibberish, punched out of half-inch-thick copper in a courtyard.The Code Even the CIA Can't Crack