Top 10 World's Uncracked Codes
That's Kryptos [wiki], a sculpture by James Sanborn on the grounds of the CIA headquarter in Langley, Virginia. The sculpture is a code, which is unsolved for over 27 years.Kryptos has four encrypted passages, three of w...
https://www.neatorama.com/2007/11/28/top-10-worlds-uncracked-codes/