- Robert Clotworthy (Narrator (voice))
- Giorgio A. Tsoukalos (Self)
- Ariel Bar Tzadok (Self)
- Jonathan Young (Self)
- David Childress (Self)
- Erich von Däniken (Self)
- Linda Moulton Howe (Self)
- David Wilcock (Self)
- George Noory (Self)
- Philip Coppens (Self)
- Nick Pope (Self)
- Mike Bara (Self)
- Bill Birnes (Self)
- Hugh Newman (Self)
- Robert M. Schoch (Self)
- Nick Redfern (Self)
Ancient Aliens — S2E4
Episode: Underground Aliens
Air Date: 2010-11-18
Runtime: 44 min
Overview
If extraterrestrials influenced human history, can evidence of their existence be found in hidden tunnels and caverns around the world? Could a cave in Ecuador contain metallic books inscribed with secrets of alien technology? Was an ancient underground city in Turkey built with alien help... or as a refuge from an alien attack? Rumors of the U.S. military working alongside aliens in a secret base inside a mesa in New Mexico continue to swirl, Native American legends mention strange inner-Earth beings, and recent archaeological discoveries in the Yucatan may point to an extraterrestrial reality behind.