Omphalos

An omphalos (ὀμφαλός) is an ancient religious stone artifact, or baetylus. In Greek, the word omphalos means "navel" (compare the name of Queen Omphale). According to the ancient Greeks, Zeus sent out two eagles to fly across the world to meet at its center, the "navel" 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. It is also the name of the stone given to Cronus in Zeus' place in Greek mythology.