KNOW THYSELF
NOTHING IN EXCESS
These were carvings at the temple of Apollo at Delphi.
From Wikipedia:
Delphi was the site of the Delphic oracle, the most important oracle in the classical Greek world, and a major site for the worship of the god Apollo after he slew Python, a dragon who lived there and protected the navel of the Earth. Python (derived from the verb pythein, "to rot") is claimed by some to be the original name of the site in recognition of Python which Apollo defeated.[2] The Homeric Hymn to Delphic Apollo recalled that the ancient name of this site had been Krisa.[3]
Apollo's sacred precinct in Delphi was a panhellenic sanctuary, where every four years, starting in 776 BC[4] athletes from all over the Greek world competed in the Pythian Games, one of the four panhellenic (or stephanitic) games, precursors of the Modern Olympics.