It used to be a mainstay of science fiction: the story where we visit a barbarian society that turns out to have been highly technologically advanced in the past. You saw this story all the time on Doctor Who and Star Trek, and in the pulps. And now, it's more or less vanished. What happened?
Top image: Michael Whelan.
We talked about this sort of story archetype with Michael Chabon, when we interviewed him about John Carter last year. We asked him where that type of "visiting a formerly advanced culture" story comes from, and he responded: