In the 21st century, mainstream scholars, scientists, and world governments have for the first time openly joined the hunt for intelligent life beyond Earth. But while such an effort has never been made public before, in reality, the search for proof of extraterrestrial life has been underway for decades. Starting around 1947, a series of unexplained sightings and mysterious events forced certain high-level members within the US government to officially become alien hunters. Projects Sign, Grudge, and Bluebook were government programs to research UFO sightings--and by some accounts, literally hundreds of the reported events were unable to be explained. Ancient Astronaut theorists suggest there is evidence that similar endeavors were even made thousands of years ago, sighting ancient astronomical observatories found all over the world, and new evidence that Babylonians were tracking the movements of the planets over 2,000 years ago.

Artificial metallic objects dating back hundreds of thousands of years. New discoveries of metals once thought to be mythological. Mysterious metal spheres defying the laws of physics. Could these out of place artifacts be physical evidence of extraterrestrials visiting planet Earth in the distant past, leaving behind remnants of their technology? Ancient Astronaut Theorists Erich von Daniken and Giorgio A. Tsoukalos travel to Romania to take a closer look at an ancient aluminum wedge that has left historians baffled. And investigative journalist, Linda Moulton Howe, travels to Jacksonville, Florida to uncover the secrets of a strange metallic sphere that fell from the sky and garnered the attention of the U.S. Navy. Might evidence of our extraterrestrial past be found in these mysterious and ancient metal objects?

In the southwest corner of the Wiltshire, England countryside lies the mysterious structure known as Rudloe Manor. On the surface, it appears to be nothing more than a quaint English manor house, but researchers have argued for years that it has been the epicenter of British research into UFOs since World War II. British Ministry of Defence (MOD) insiders claim that an astounding 2.2 million square feet of vast caverns divided into many smaller chambers lie buried underneath Rudloe Manor. Giorgio A. Tsoukalos and Nick Pope explore the possibility that important files related to the history of the UFO phenomenon are being kept under lock and key here. Might recovered extraterrestrial craft be stored and analyzed there as well? Could the evidence of extraterrestrial contact from the Berwyn Mountains incident in 1974 and the Rendlesham forest encounter in 1980 be hidden in this highly protected facility?

Many of the architectural marvels of the ancient world bear striking similarities to one another, even though they were built by civilizations that were separated by thousands of miles and are believed to have had no contact with one another. Separated by more than 7500 miles, the Giza pyramid complex in Giza, Egypt and the Avenue of the Dead in Teotihuacan, Mexico contain pyramids that are aligned with the constellation of Orion's belt. An ancient pyramid temple in Cambodia known as Baksei Chamkrong is an almost identical match for the Temple of the Jaguar in Guatemala. Many structures built using stone slabs that weighed over a hundred tons. But how did primitive people achieve such extraordinary feats? And why do we see such similarities? Could these sites have all been designed by alien architects?

According to legend, an ancient curse was placed upon the tomb of King Tutankhamun, and when that tomb was opened in 1922, a series of terrible events occurred. A curse was also placed on King Tut's father Akhenaten, and during the rehearsal of a play dramatizing the lifting of this curse, similar tragedies followed. Could a curse truly exist, but in the form of alien technology that is protecting an incredible secret about our past? Is there hidden power in the words inscribed on so-called "magic bricks" found in King Tut's tomb, or in those contained in the play to lift Akhenaten's curse that are connected to some extraterrestrial force? Ancient Astronaut theorists suggest that The Pharaohs' Curse was put in place to protect not only the truth about an otherworldly event in our past, but also an extraterrestrial device--a device that some believe still exists today, buried deep beneath the Earth... on Oak Island.

Nearly every year archaeologists and anthropologists make discoveries that require revisions to our history books. But there are numerous artifacts that are outright ignored because they don't fit into the accepted scientific paradigm. Could clues about our extraterrestrial origins be hidden in these discarded pieces of our past? Shocking evidence has recently been revealed that challenges the accepted dating of the Great Pyramid. An ancient hammer found in Texas that dates back 140 million years is ignored by mainstream archaeologists. And unexplainable elongated skulls have been found on nearly every continent of the world that science refuses to test. Could we be on the brink of scientific discoveries that the academic community cannot deny? Evidence that reveals the truth of where we really came from, why we are here and if we are alone in the Universe?

The ancient site of Teotihuacan in central Mexico--which the Aztecs called the "City of the Gods"--is one of the world's greatest mysteries. To this day, no one knows who built the metropolis or what happened to its occupants, but based on evidence that has recently been unearthed, Ancient Astronaut theorists suggest it was once home to a highly advanced, perhaps extraterrestrial, civilization. The many structures that still stand in Teotihuacan appear to be encoded with advanced mathematical and cosmic principles, and the layout precisely mirrors the positions of the planets in our solar system. Modern excavations at the site have unearthed discoveries of liquid mercury, walls lined with mica, and strange golden-spheres containing unknown substances--all of which are out of place in the ancient world. Could these artifacts be the remnants of an alien society? Perhaps even an extraterrestrial spaceport?

The use of mantras and chanting to connect with a higher plane has existed in cultures all over the world dating back thousands of years, but why would people who had no contact with each other all subscribe to this practice? Could there be certain frequencies that connect us with greater--perhaps extraterrestrial--forces? Researchers have found that dozens of megalithic sites stretching across the globe--like the prehistoric Newgrange monument in Ireland, the chiseled labyrinths underneath the island of Malta, and the giant temple complex of Angkor Wat in Cambodia--were all designed to emanate the exact same frequency. The planets in our solar system each give off a distinct sound, and certain places on Earth, like Taos, New Mexico, have been found to produce a hum from an unknown source. Might the best evidence of alien intervention on Earth be found not with our eyes... but with our ears?

In 1984, a roll of 35mm film surfaced from an anonymous source that contained pictures of what is now known as the Eisenhower Briefing Document. This document is purported to be a memo sent from the director of the CIA in 1952 to president-elect Dwight Eisenhower, informing him of the existence of a top-secret group within the US government called "The Majestic Twelve." Composed of top scientists, government officials, and military elite, this group's mission was to investigate reports of unidentified flying objects--and to examine crashed extraterrestrial craft. And more recently, in 2002, a major computer hack into Pentagon and NASA computers appears to reveal hard evidence that not only are the Majestic Twelve documents real, but that the government's interaction with extraterrestrials has led to the creation of a secret space program, that has already established bases on the moon, Mars, and other celestial bodies.

Throughout history, prophets and visionaries have claimed to be able to telepathically access knowledge and information that would ultimately steer the course of human history. But if true, where do these individuals get their visions? According to ancient mythologies, there is a universal repository of knowledge known as the Akashic Record. While most mainstream scholars relegate this to the realm of mythology, recent scientific discoveries have opened the possibility that such a repository could actually exist--and is accessible by the human mind. Giorgio A. Tsoukalos meets with neuroscientist Dr. Dario Nardi to measure the brainwaves of Dr. Deepak Chopra as he enters a state of deep meditation to observe the physical chnges in the brain as he connects or taps into something beyond ourselves. Could our ability to tap into the Akashic Record lead to the next giant leap in human evolution--and connect us to other intelligent beings throughout the cosmos?

India's Sanskrit texts are filled with incredible stories about advanced technology in the ancient world. Highly complex building techniques, brain surgery, flying crafts, and even nuclear physics are described with uncanny accuracy. Hindu scholars attribute this knowledge to a time when "gods" walked among men. Might this period of time actually be referring to an age when extraterrestrials inhabited the planet? Giorgio A. Tsoukalos travels to India to further explore the Sanskrit texts, as well as the structures and technology that have stood the test of time. From a temple that inexplicably survived a major earthquake to evidence of ancient brain surgery and instructions for advanced flying machines, Giorgio studies the sacred knowledge that is said to have come directly from the voices of the gods.

Extraterrestrials are almost always envisioned as humanoid, but is this an egocentric concept? Could it be that intelligent alien life looks much different from us, and that some extraterrestrials more closely resemble other animals? And is it possible that many of the animals that roam the Earth have otherworldly origins? By examining ancient cultures around the world, we find that nearly all revered certain animals and depicted their gods with animal traits. The Sanskrit epics of India feature gods in the form of elephants, monkeys, and snakes. The Sumerians depicted gods with bird heads and wings. And in Egypt, not only did they portray many of the gods with animal features, but they even went so far as to mummify their animals. Ancient Astronaut theorists suggest that certain animals may not have developed through Darwinian evolution, but were planted here by alien visitors.

Across the globe, over 1.5 billion people believe in reincarnation, the belief that a soul can be reborn into a different body after death. Major universities worldwide have departments devoted to the study of reincarnation and according to their research there is a mounting body of evidence that suggests some people have the ability to vividly recall past lives. Ancient Astronaut Theorists suggest that not only does reincarnation exist, but our extraterrestrial ancestors specifically designed the human body to be a vessel for otherworldly entities. World leaders, like the Dalai Lama and even Saddam Hussein, claim to be the reincarnations of powerful figures from the past–figures with an extraterrestrial connection. If souls are indeed recycling through various embodiments, is this simply the natural continuation of life–or might this process be directed towards some greater end? One that reaches far beyond Earth?

In Honshu, Japan, stands one of the country's oldest and holiest Shinto shrines--the Ishi-no-Hoden megalith. Carved from a single rock and weighing roughly 500 tons, it appears to hover over a pool of water, and according to Japanese legend, it was built to depict a sky ship made of stone that the ancient people witnessed descending from the heavens. Ishi-no-Hoden is just one of numerous megalithic structures found throughout Japan commemorating a time when the gods--or, perhaps, extraterrestrial beings--descended to Earth. Centuries old texts describe in vivid diagrams strange craft that have appeared in the sky and on the shores. And satellite images of Mars have revealed keyhole-shaped structures identical to some of Japan's oldest tombs. Could Japan's origins lie beyond Earth, and might a surge of recent UFO sightings provide clues that the island nation provides the key to reconnecting mankind with its extraterrestrial past?

Hundreds of strange disks are discovered in a cave in China that appear to tell the story of an ancient extraterrestrial crash on Earth. Shortly after the disclosure of these artifacts, the disks are confiscated by the Chinese government and dismissed as a hoax. But are they? Ancient traditions from around the world speak of mysterious disk-shaped artifacts that held tremendous power. The Babylonians claimed to have a disk that stood in for their most powerful deity. The Incan leader Pachacuti attributed his rise to a divine disk that fell from the sky. And treasure hunters have been searching for centuries for the acclaimed “Golden Sun Disk” that was hidden from the Conquistadors when they sacked Peru. Ancient Astronaut theorists propose that these disks were more than just sacred objects, and represent some sort of extraterrestrial technology.

The ancient site of Gobekli Tepe challenges everything modern archaeologists believe about mankind's past. The megalithic stone complex was built over 12,000 years ago, which dates it to 6,500 years before Stonehenge, and 5,000 years before the first known civilization was said to have emerged in Mesopotamia. Mainstream archaeologists believe that humans were roaming the Earth as simple hunter-gatherers at this time, but if so, how could they have built such incredible structures? Might they have had help from a more advanced - perhaps extraterrestrial - civilization? According to Ancient Astronaut Theorists, the site serves as the smoking gun for a lost civilization - one whose survivors may have built the site to preserve important information about otherworldly visitors. Does the site offers clues about our extraterrestrial past that the ancients felt compelled to preserve for future generations?

Studies have shown that up to 70% of all UFO sightings happen in so-called ‘hotspots’ where reports of visions, mysterious lights and unusual phenomena are regularly witnessed–and not only in modern times, but dating back thousands of years. Could there be something about these locations that attracts extraterrestrial visitors?

More than 10,000 crop circle formations have been documented in over 50 countries, and many display properties that defy conventional explanations. Are they of otherworldly origin? And if so, what is their purpose? Could it be that reconnection with our alien ancestors will only come when we finally crack the crop circle code?

The discovery of the ancient megalithic site of Karahan Tepe in southern Turkey turned the world of archaeology on its head, displaying engineering skills far beyond what the people of the time were thought to be capable of. But could new evidence reveal that this more than 11,000-year-old complex was built not by humans…but giants?

The towering obelisks of ancient Egypt weigh hundreds of tons and each was perfectly carved from a single granite rock. While mainstream scholars identify them as monuments to the pharaohs, Ancient Astronaut Theorists suggest they may have served a technological purpose–they powered a technology that allowed for communication with the gods who came from the stars.

The Mutual UFO Network is an organization devoted to the scientific investigation of unidentified aerial phenomena and other unexplained encounters; with more than five decades of investigations, MUFON's extensive database could contain proof.

Meteor impacts have significantly altered our world, creating the perfect environment for the rise of humankind and delivering metals essential to the development of an advanced civilization. But could new evidence reveal that celestial objects have been directed to Earth by an alien intelligence?

The Center for the Study of Extra-Terrestrial Intelligence defines a “Close Encounter of The Fifth Kind” as direct human contact and communication with extraterrestrial life. But is this a classification that will only be useful in the distant future, or have such encounters already taken place… and within the highest levels of the U.S. government?

The vast Alaskan wilderness is known for mysterious disappearances, electromagnetic anomalies, stories of strange creatures and UFO sightings; Alaska's many mysteries could be due to a presence that is not of this world.

Terrifying encounters at 40,000 feet. Pilot accounts of UFOs taking control of their aircraft. Entire jumbo jets disappearing into thin air. Since the dawn of aviation, pilots have experienced unexplainable events in the sky. Could they have witnessed aliens in our airspace?