Sator Square

The Sator Square (or Rotas Square) is a word square containing a Latin palindrome:

S A T O RA R E P OT E N E TO P E R AR O T A S

The five words may be read top-to-bottom, bottom-to-top, left-to-right, or right-to-left. When read top-to-bottom and left-to-right, it forms a Latin palindromic sentence:

SATOR   AREPO   TENET   OPERA   ROTAS

The earliest dateable Sator Square was found in the ruins of Pompeii, which was buried in the ash of Mount Vesuvius in 79 AD. Examples may be found carved on stone tablets or pressed into clay before being fired. Its translation has been the subject of speculation with no clear consensus.

(- From Wikipedia)