Along the wall enclosing the remains of a castle is an unusual stone. It is squared-shaped, and it bears a grid with the following words readable both horizontally and vertically: SATOR, AREPO, TENET, OPERA, and ROTAS. These words can be read backwards, so that SATOR is ROTAS written backwards, AREPO is OPERA written backwards, and TENET, being at the middle of the five-letter square, is a palindrome itself. Another feature of this stone is that the initials of these five words spell out SATOR, the second letters of these words…
