Have we been visited by extraterrestrial beings? Did these "ancient aliens" contribute to the birth of human civilization? Do our ancient monuments contain evidence of their presence?

In this exciting documentary you'll join a small team to the Bosnian city of Visoko. They've heard of a man called Semir 'Sam' Osmanagich. He claims to have discovered huge old pyramids, a vast network of underground tunnels and an ancient tumulus. For four and a half days he guided our team around, in search of proof of his claims. The Bosnian Indiana Jones, as Osmanagich is nicknamed, promised to show our camera crew the best places. So it would be definitive once and for all that there really are pyramids in the Bosnian Visoko valley. But are there? Or is it the biggest hoax in history?

Did intelligent beings from outer space visit Earth thousands of years ago? From the age of the dinosaurs to ancient Egypt, from early cave drawings to continued mass sightings in the US, each episode gives historic depth to the questions, speculations, provocative controversies, first-hand accounts and grounded theories surrounding this age old debate.