My favorite ancient civilization is what Plato called, "Atlantis."
We don't know what they called themselves or their land, but it might have been similar to the Greek name given them -- perhaps "Atlan" or "T'Lan."
Scientists have egos and they easily get bruised, especially when talking about something for which there is a great deal of "ridicule inertia." Take the "Clovis first" fiasco, for instance. Ridicule was so thick that scientists were afraid to dig below the Clovis horizon for years. Atlantis is a far more potent "blasphemy."
But we have evidence for Atlantis. Tons of it. Nothing direct, yet, but plenty of indirect evidence.
We now know that something very big occurred that changed the world right when Plato said Atlantis was swallowed by the sea. In fact, one piece of scientific evidence is a veritable smoking gun in the death of Atlantis.
The real Atlantis may have had advanced technology -- flight, but using other technology, perhaps even the manipulation of space itself. Many of our legends and myths hint at this.