Aliens and the Secret Code (S03E13)

Megalithic monuments linked together by electromagnetic energy... Prehistoric ruins arranged across vast distances in straight lines... And advanced mathematics carved into landmarks more than 5000 years ago. Were ancient man's spectacular structures built by humans alone? Or do they bear evidence of being designed - and interconnected - by otherworldly visitors? Could there be a World Grid that links Earth's energy vortexes, ancient sites, and star alignments? And if so, might ancient extraterrestrials have left behind a secret code embedded in the mysterious grid? What might they have wanted to tell us? (iTunes)