What if life on Earth began in outer space? Millions of people accept the theory that intelligent life forms visited Earth thousands of years ago and were worshipped as gods by primitive man. Are monuments like Stonehenge and Easter Island the last remains of an ancient alien visitation? From unexplainable super structures, to knowledge of the solar system, mathematics, and even the ability to make electricity, this special explores evidence of super-human influences on ancient man and embarks on an around-the-world search for answers. It's an investigation into a theory some believe cannot be true, but many agree cannot be ignored.

Tales of angels and giants in the ancient world are examined to determine if the beings stem from mythology or extraterrestrial visits and experimentation on human DNA, and bizarre discoveries around the world may be the key to getting the answers.

Series host and Ancient Astronaut theorist, Giorgio Tsoukalos, explores the mystery of the Nazca Lines found in the desert region of Southern Peru. Hundreds of gigantic lines, some in the shape of animals, geometric patterns and even an alien-like being, extend for miles over a vast section of the arid plain. Scholars are divided as to who built them, and why. Some Ancient Astronaut theorists believe that the massive markings have an extraterrestrial connection, and perhaps the ancient people of the region created these gigantic figures in tribute to the gods who visited them. While the area was abandoned nearly 2000 years ago, remains of ancient Nazca people have been found with strange, elongated skulls. Could this be evidence that there really was contact with "sky people" as ancient legends describe?

Ancient Astronaut theorist, Giorgio Tsoukalos, shares his insight on massive stone structures and strange, giant figures known as Monoliths. What compelled ancient man to move colossal stones, in some cases weighing thousands of pounds, and to build remarkably similar stone monuments all around the world? From the jungles of Costa Rica to England's rural countryside, ancient people achieved extraordinary feats of construction without advanced tools or technology. Is it possible that extraterrestrials instructed the ancients to build these complex structures? Or were our ancestors driven to create these monoliths in order to reconnect with celestial travelers who once walked the Earth? Could ancient monoliths hold advanced, extraterrestrial powers we have yet to realize? And if so, just what will happen when we unlock the mystery of the monoliths?

Giorgio Tsoukalos presents the fascinating story of Nikola Tesla, one of the most prolific inventors of the 20th century--and the man that actually electrified the world. Tesla is credited with shepherding mankind to a new industrial era and laying the groundwork for today's technological age. The genius inventor claimed he could visualize his inventions in full-detail and manipulate them in his mind. And he also claimed to have direct communication with intelligent beings on other planets. Is it possible that this alleged mad scientist, so far ahead of his time, was actually a human "receiver"? A being tapped to advance mankind--and pave the way for a future reunion with our alien ancestors?

Did our ancestors have an understanding of how to generate power thousands of years before modern man? Ancient Astronaut theorist, Giorgio Tsoukalos, theorizes that some of the most famous ruins on Earth may be long-forgotten power sources that hold a celestial connection. From the discovery of an ancient battery in Iraq and the depiction of a primitive light bulb in Egypt, to a wireless power grid that may have reached around the world, there is evidence suggesting ancient man had access to electricity, which, until recently, was believed to be a modern day phenomenon. But if our ancestors did possess power, where did they gain this knowledge? Is it possible that they received this wisdom from an extraterrestrial source as ancient astronaut theorists contend? And, if so, why did the power stop flowing?

Ancient Astronaut theorist, Giorgio Tsoukalos explores one of the most compelling and mysterious locations on Earth, Puma Punku. Forty miles west of La Paz, Bolivia--high in the Andes Mountains--lie the mysterious ancient ruins of Puma Punku. Spread across a desert plateau at an altitude over 12,000 feet, the megalithic stones found scattered here are among the largest on the planet. Mainstream scientists believe native people used primitive stone tools to construct the site approximately 2000 years ago. But in 1945, archaeologist Arthur Posnansky proposed that Puma Punku was much, much older--perhaps going back to 15,000 BC. And Ancient Astronaut theorists point to the intricate stonework and interlocking qualities of the megalithic stone blocks as evidence of the use of advanced technology--technology of an otherworldly origin. Could Puma Punku have been built by extraterrestrials?

Giorgio Tsoukalos decodes some of the most compelling evidence for Ancient Astronaut theory found in mysterious carvings, symbols, and structures that are strikingly similar on opposite ends of the Earth. Egyptian pyramids aligned with the stars of Orion's belt match up perfectly with pyramidal structures in Central Mexico. A sacred symbol common to India appears carved into the desert floor of Peru. And a modern day crop circle in England is an identical match for a design carved on a stone found just outside Roswell, New Mexico. Is this mere coincidence? Or could the answers to mankind's greatest questions about our origins and our future actually be hidden in plain sight, disguised in the form of alien messages?

Ancient Astronaut theorist, Giorgio Tsoukalos, explores the construction, history and technological abilities of the Ark of the Covenant--one of the most sought after religious relics of all times and far more than just a box that contained the Ten Commandments. The biblical stories surrounding the Ark speak of a device with divine powers that was able to produce food, take down stonewalls, kill those that come in contact with it, and provide direct communication to God. Are these stories mere myth? Or did the Ark of the Covenant possess extraordinary powers? Just what was this incredible device? Were its powers the result of divine miracles? Or were they the product of advanced, extraterrestrial technology?