Behold: Kryptos. A Linguistic Lock with 870+ Tumblers.

http://en.wikipedia.org/wiki/Kryptos

This is just fascinating.  Imagine the work Sanborn put into designing this.

A quote from Wikipedia: 

"Kryptos is a sculpture by American artist Jim Sanborn located on the grounds of the Central Intelligence Agency (CIA) in Langley, Virginia. Since its dedication on November 3, 1990, there has been much speculation about the meaning of the encrypted messages it bears. Of the four sections, three have been solved, with the fourth remaining one of the most famous unsolved codes in the world. The sculpture continues to provide a diversion for some employees of the CIA and other cryptanalysts attempting to decrypt the messages."


You can visit the CIA website about Kryptos HERE:
https://www.cia.gov/about-cia/virtual-tour/kryptos/index.html

Kryptos.  The name says it all.  Just look at it.

The beauty is...  Mind-boggling.  Simply staggering.  This is the kind of puzzle that gives cryptographers - professional or otherwise - nightmares... or revelations.

There are four parts to this masterpiece, four riddles, each leading to the next answer.  See if you can make sense of it.  Please note that everything here is written exactly as it appears in the translations.  Some words might seem to have an odd spelling - Sanborn has admitted this was largely due to aesthetic impulse.  Nonetheless, the message (whatever it might be!) gets through.

1) BETWEEN SUBTLE SHADING AND THE ABSENCE OF LIGHT LIES THE NUANCE OF IQLUSION

2) IT WAS TOTALLY INVISIBLE HOWS THAT POSSIBLE ? THEY USED THE EARTHS MAGNETIC FIELD X THE INFORMATION WAS GATHERED AND TRANSMITTED UNDERGRUUND TO AN UNKNOWN LOCATION X DOES LANGLEY KNOW ABOUT THIS ? THEY SHOULD ITS BURIED OUT THERE SOMEWHERE X WHO KNOWS THE EXACT LOCATION ? ONLY WW THIS WAS HIS LAST MESSAGE X THIRTY EIGHT DEGREES FIFTY SEVEN MINUTES SIX POINT FIVE SECONDS NORTH SEVENTY SEVEN DEGREES EIGHT MINUTES FORTY FOUR SECONDS WEST X LAYER TWO

3) SLOWLY DESPARATLY SLOWLY THE REMAINS OF PASSAGE DEBRIS THAT ENCUMBERED THE LOWER PART OF THE DOORWAY WAS REMOVED WITH TREMBLING HANDS I MADE A TINY BREACH IN THE UPPER LEFT HAND CORNER AND THEN WIDENING THE HOLE A LITTLE I INSERTED THE CANDLE AND PEERED IN THE HOT AIR ESCAPING FROM THE CHAMBER CAUSED THE FLAME TO FLICKER BUT PRESENTLY DETAILS OF THE ROOM WITHIN EMERGED FROM THE MIST X CAN YOU SEE ANYTHING Q (?)

4) People are still figuring this out.  The CIA hasn't broken the code.  These are the people who were behind the cracking of the German Enigma device back in WWII.  And here, a "mere" artist (a true genius!) has outsmarted them since 1990.  Amazing.

Note that each individual incidence of X appears (to me) to be the equivalent of a STOP in a telegram.  Most curious is the passage:

THIRTY EIGHT DEGREES FIFTY SEVEN MINUTES SIX POINT FIVE SECONDS NORTH SEVENTY SEVEN DEGREES EIGHT MINUTES FORTY FOUR SECONDS WEST

Those are coordinates. 

Look them up on Google Maps.

Simply Amazing.