4-th episode of 2-th season "Ancient Aliens"

What "Ancient Aliens" 4-th episode about

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?

Episode number: 4

Episode name: "Underground Aliens"

Episode release date: 19 november 2010 at 03:00

Status: aired

Rating: 7.2