The omphalos is a very common type of religious stone artifact/ tablet. The word omphalos means "navel" in Greek. According to the ancient Greeks, Zeus sent out two eagles to fly across the world and they met at its center, the "navel" of the world - which the omphalos represents.
Many records indicate that the omphalos stone was the holiest object at various oracle centers in all the lands bordering the Mediterranean Sea, the most well known being at Delphi. It most likely originated from the "stone of splendor" associated with the Canaanite god Baal. The main characteristic of the omphalos/stone of splendor was its ability to allow direct communication with the gods.
Most accounts locate the Omphalos in the temple adyton near the Pythia. The stone itself (which may have been a copy) has a carving of a knotted net covering its surface, and has a hollow centre, which widens towards its base. The Omphalos at Delphi came to be identified as the stone which Rhea wrapped in swaddling clothes, pretending it was Zeus. This was to deceive Cronus, his father, who swallowed his children so they could not grow up and depose him as he had deposed his own father, Ouranos.
Omphalos stones were said to allow direct communication with the gods. Leicester Holland (1933) has suggested that the stone was hollow to channel intoxicating vapours breathed by the Oracle. Erwin Rohde wrote that the Python at Delphi was an earth spirit, who was conquered by Apollo, and buried under the Omphalos, and that it is a case of one god setting up his temple on the grave of another. Christian destruction of the site in the fourth century at the order of Emperors Theodosius I and Arcadius makes all suggestions about its use tentative.
Jerusalem: In the Church of the Holy Sepulchre in Jerusalem there is also an omphalos. The existence of this stone is based upon the medieval cosmology which saw Jerusalem as the spiritual if not geographical center of the world (see T and O map). In fact, this tradition is likely based on an ancient Jewish tradition that saw Jerusalem as the navel of the world.
In the Jewish tradition, the Ark in the Temple in Jerusalem, through which God revealed himself to His people, was located on a Foundation Stone located on the Navel of the World. (This Jewish tradition is known to have begun in Hellenistic times, when Jews were already quite familiar with Greek culture - and thus, might be a deliberate emulation of and competition with the above tradition regarding Delphi).
Hebrew Tree of Life