The Omphalos Stone currently in the Archaeological Museum in Delphi.
In Greek mythology, Zeus sent two eagles to fly across the world to meet at its centre, the “navel” (Greek: ὀμφαλός) of the world.
Omphalos stones used to denote this point were erected in several areas surrounding the Mediterranean Sea; the most famous of those was at the oracle in Delphi. Hesiod equated the omphalos stone at Delphi with the one swallowed by Kronos thinking it was Zeus (…when the due time came round, the great crooked-schemer Kronos, tricked by the cunning counsel of Earth, defeated by his son’s strength and stratagem, brought his brood back up. The first he spewed out was the stone, the last he swallowed. Zeus fixed it in the wide-pathed earth at holy Pytho, in the glens of Parnassus, to be a monument thereafter and a thing of wonder for mortal men. [Hesiod, Theogony, 493-500].