Aosta - Collegiata di Sant'Orso

The collegiate church, dedicated to Saint Ursus of Aosta, existed here already in Carolingian times. Ursus, who may have been Irish, was a missionary, who supported the Bishop of Aosta. When an Arian became bishop of Aosta, Ursus and other canons left the cathedral and settled outside the walls of Aosta at the present site of the collegiate church of Saint Ursus.

A Romanesque church was built around 1000, but this church got rebuilt, altered and enlarged many times over the centuries.

Archaeologists unearthed this mosaic in 1999 - and now it can be seen under security glass. The mosaic is dated to the first half 12th century. It depicts long-haired Samson, killing the lion.

Written around the scene are the words

S A T O R
A R E P O
T E N E T
O P E R A
R O T A S

A Latin palindrome known as the "Sator Square".

What Wiki knows about it is here:

en.wikipedia.org/wiki/Sator_Square