This is one of many of the marble inlays on the floor of Siena Cathedral.
It shows Hermes Trismegistus, a very mysterious but revered forerunner of Moses.
Early Christian theologians believed that Hermes Trismegistus was a great thinker and a pious and wise man
who had revelations from God, and that he espoused the belief in one God.
His ideas were interpreted by some of the Neoplatonists in the Renaissance.