This little word puzzle has been found in various Roman ruins, including in Pompeii:
R O T A S
O P E R A
T E N E T
A R E P O
S A T O R
Rearrange the words, and you get this “Paternoster” (“Our Father”) cross form with “A” — alpha and “O” — omega at each tip:
A
P
A
T
E
R
A P A T E R N O S T E R O
O
S
T
E
R
O
Apparently no one is sure of its purpose. The early Christian use of symbols like this is fascinating to me. I wish evangelicals weren’t so stingy with symbolism. I guess one similar thing we sometimes use is the Christian fish on our cars.