The only serious rival to Zeus in importance was the great god Apollo. Sometimes known as Phoebus (Brilliant Light), Apollo was associated with the sun, with light, with music and medicine, and with reason and self-knowledge. His centers were in Delos, where he was said to have been born, and Delphi, the navel of the world in the Greek view of things, and a place of prophecy sacred to him. It was near Delphi, at the foot of Mount Parnassos, that Apollo killed Python, the great serpent that guarded the sanctuary, which was sacred to the ancient earth goddess Gaia. By killing the dragon-like Python, Apollo became the dominant figure in Delphi.