Scale

"Prometheus Bound (whose Aeschylean authorship has been disputed) is about the result of Prometheus's gift of fire to the human race, in order to save them from extermination planned by the tyrannical Zeus. We find Prometheus chained to a rock upon the Caucasus for evermore, as a divine punishment for what he has given to humanity. Addressing Io, Zeus's mistress condemned to wander the world, he prophesies that in the distant future a descendant of hers will free him. And the rest of the trilogy, which is lost, apparently led to his liberation, after thirty thousand years."
The Founders of the Western World- Michael Grant

Aeschylus pounds out his ideas with an aide:

"We've got to put Prometheus somewhere far away."
"Somewhere epic."
"Yeahhh."
"Ooh! I got it! How about... the Caucasus?"
"Damn! Isn't that where Miletus's colony is? That is pretty far away... That's gotta be a good couple hundred miles."
"OK, now how long should he stay chained up there?"
"Um, let's not make it too long. We want to finish this story off in a trilogy, you know."
"How about, say, thirty thousand years?"
"Thirty thousand? Yeah, that sounds pretty reasonable."