The Sator Square

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

The Sator Square is a word square containing a Latin palindrome featuring the words SATOR AREPO TENET OPERA ROTAS written in a square so that they may be read top-to-bottom, bottom-to-top, left-to-right, and right-to-left. The earliest known appearance of the square was found in the ruins of Pompeii which was buried in the ash of Mt. Vesuvius in 79 AD. If the Sator Square is read boustrophedon, with a reverse in direction, then the words become SATOR OPERA TENET, with the sequence reversed.^[1]