Painting from the interior of a kylix (wine cup) from Ionia (570-560
B.C.), now in the Louvre Museum, showing Zeus sitting on the throne
and facing an eagle with outspread wings. The eagle, the bird which
flies above any other, was an attribute of Zeus, in his manifestation
as Zeus Hypsistos (“the Highest”, “Who Stays Above”).
Besides being Zeus’s messenger, the eagle had the duty to bring
to the god his lightning, with which he manifests his power. Sometimes,
Zeus transforms himself into an eagle, as in the case of Ganymede’s
abduction, in which the boy was brought in the sky to live forever among
the immortals as cup-bearers for the gods of Olympus.
[Source: http://library.artstor.org/library/]