Mount Olympus was a mountain in the ancient nation-state of Greece, located in Europe's Mediterranean region on Earth. It figured heavily in the universe of Greek mythology as the home of the gods.
In reality, these gods were aliens with psychokinetic abilities that made them god-like to ancient Greeks. After Humans outgrew the need for such gods, they fled Olympus to Pollux IV.
In 2267, attempting to bring Carolyn Palamas back from her reverie regarding Apollo, James T. Kirk remarked, "All right, lieutenant, you can come down from Mount Olympus now. You've got work to do." (TOS: "Who Mourns for Adonais?")