Kryptos Sculpture

This sculpture was made by Jon Sanborn was placed in front of CIA headquarters at Langley, Virginia, and has remained unsolved since 1990.
3 out of 4 sections, K1, K2, and K3 three have been solved, but K4 has eluded all cryptographers.
More recently, Sanborn announce a clue, BERLIN, in hopes that he would still be alive to see the statue solved.
The story of the sculpture is fascinating.
Full text of the sculpture can be found here and if you think you've solved the 97 character K4, you can submit your answer here
Seriously, czech it out.