The Mayan civilization dominated Central America for nearly 2000 years, but by the 9th century A.D., the great Mayan cities were abandoned, and the Mayan people vanished. What could have happened to this advanced culture? Might the Maya have left clues as to how they surpassed other cultures in science, mathematics, time keeping, and most importantly, astronomy? In recent years, hieroglyphs have been decoded to reveal that the Maya were able to accurately predict shifts in the Earth's axis every 26,000 years. Inscriptions on the sarcophagus of their most prominent ruler, King Pakal, tell of a journey to the Milky Way. And a sophisticated calendar foretells of the end of the world in 2012. Most striking is their belief that knowledge was passed to them by otherworldly beings who descended from the sky. Could the ancient Maya have actually conspired with extraterrestrial visitors to plan the future--and even the very end of the world?

The Maya created the most sophisticated calendar systems in the ancient world, and according to many scholars their Long Count Calendar will come to an end on December 21, 2012. What does this mean for mankind? Some researchers believe it will usher in the return of Bolon Yokte--a mysterious god associated with creation and war. Could this god actually be an extraterrestrial as some ancient astronaut theorists believe? Other scholars believe the end of the calendar will bring about a series of catastrophic events that may threaten the very existence of mankind. They point to a rare galactic alignment that will coincide with the end of the Mayan calendar as proof of an impending geological catastrophe. If these doomsday prophecies prove to be true, will it mean the end of the world as we know it? Or could it reveal some profound truth about the origins of the human race?

Who are the beings with big heads and giant eyes that seem to have been visiting our planet for millennia? Known by researchers as the "greys," these mysterious beings have been depicted in rock-art and carved stone figures throughout the ages and all over the world. Who are they, what planet do they come from, and what do they want?

There are numerous historical, religious and mythic accounts of ancient civilizations being wiped out by volcanoes, earthquakes, floods, and meteors. Did god, or nature bring about such disasters? Or is it possible that celestial beings had a hand in the ancient world's catastrophic disasters?

NASA scientists, former astronauts and secret government files all point to the conclusion that there has been contact with extraterrestrial life in the past. Researchers examine this and other recent scientific evidence that may provide proof of alien contact in both the recent and ancient past.

At nearly 14,000 years old, the ruins of Puma Punku are the oldest and most baffling on the face of the Earth. No one knows who designed and built this complex of sophisticated inter-locking blocks, and then vanished. Researchers investigate the ruins on-location in Peru and present new computer analyses. Forensic evidence on the ground, together with local myths and legends, suggest this site may have been designed and even once inhabited by a species of extraterrestrials.

People on every continent have claimed to see the footprints of Bigfoot. And ancient myths and legends speak of an ape-like giant stalking the earth. What if, as Ancient Astronaut theorists believe, there is evidence to connect Bigfoot with an alien species that once visited Earth in the distant past?

Might an examination of Leonardo Da Vinci's masterful paintings, highly technical hand-drawn sketches, and private journals reveal knowledge of otherworldly technology and extraterrestrial beings?

Is it possible that sightings of alien beings or UFOs may actually be evidence of time travelers from the future? And might ancient astronauts actually be time travelers from our future? Scientists explore the theoretical possibility of time travel. How can it be achieved? And what might people from 10,000 years in the future look like?

Angkor Wat, Cambodia, is the world’s largest ancient religious temple. Within its megalithic ruins, researches have discovered a depiction of a species of dinosaur – a stegosaurus. But how could the ancients have had knowledge of animals that mainstream science says died out millions of years ago? Why are dinosaurs extinct? Did an alien race of beings kill off the dinosaurs to make room for humankind?

Did a biblical patriarch receive instructions from 200 Angels high above the earth? Were the ancient Greeks taught how to work metal by a race of fish-people? And might Egypt's most controversial Pharoah have been an extraterrestrial being? Giorgio Tsoukalos looks at mysterious teachers who have appeared throughout history and reveals The Top Ten Alien Influencers who he believes provide the ultimate proof of extraterrestrial contact...

For more than a decade, Ancient Aliens has collected dozens of reports of encounters with strange and mysterious beasts. Now, Ancient Astronaut Theorist Giorgio Tsoukalos takes a look back at The Top Ten Extraordinary Creatures we've investigated--creatures that just might provide compelling evidence of extraterrestrial visitation...

This episode promises a countdown of the most unsettling and enigmatic incidents that suggest possible visitations from beings beyond our world. From a perplexing incident in rural Texas that left witnesses with unexplainable injuries to the eerie phenomenon of mysterious cattle mutilations, each story unfolds to explore the possibility of extraterrestrial involvement. With a mix of firsthand accounts, expert analysis, and chilling reenactments, “Ancient Aliens” delves into the uncharted territories of unexplained phenomena, leaving viewers on the edge of their seats as they contemplate the mysteries that may lie beyond the stars.

Ancient Aliens is counting down ten of the most intriguing--and mysterious--symbols and codes found across the globe that just might contain proof of otherworldly contact. From glyphs in the Peruvian desert, to spiral petroglyphs embedded with advanced math, and a language with an otherworldly origin, could these codes unlock the secrets of our extraterrestrial past?

Ancient Aliens is counting down the top ten most devastating disasters ever documented that might have an otherworldly connection, from a flying monster at a nuclear incident, a meteor that wiped out the dinosaurs, and a deadly virus that might be from another world. Could these disasters be proof of extraterrestrial contact?

More than 7,000 years ago, the ancient Sumerians established what is considered the world's first civilization and they credited their extraordinary achievements to their gods, the Anunnaki. But is it possible that these powerful beings were, in fact, extraterrestrial visitors to Earth?

Along the Earth's north 37th parallel there have been so many reports of unidentified flying objects, animal mutilations, and other mysterious events that it has been dubbed The UFO Superhighway. Could there be something about this latitude that is attracting extraterrestrial visitors?

For thousands of years, Scotland has been an epicenter of otherworldly phenomena; it is home to mysterious ancient stone circles, stories of strange beings, and is a major hotspot for UFO sightings.

Throughout the world there are mysterious ancient stones shaped into perfect spheres; many of them show clear evidence of being manmade and some completely defy explanation; the mystery of the stone spheres could provide clues about humankind's past.

Considered by many to be the greatest civilization in the history of the Americas, the Maya thrived for more than 2,000 years. Now, new evidence is being discovered that completely upends our understanding of this ancient culture... and might provide evidence that the Maya came in contact with extraterrestrial visitors.

For thousands of years, cultures around the world have held a belief in stargates through which beings have traveled to Earth from distant points in the universe and even other dimensions. Could such portals truly exist? And if we obtain the key to unlocking the stargates, will we find a cosmos teaming with life?

For decades, incredible claims have been made about an extraterrestrial presence on Earth, and the government has gone to great lengths to discredit them.

For thousands of years, humankind has attempted to make contact with beings from beyond Earth; now, the search for extraterrestrial intelligence is ramping up, with new technologies allowing individuals to explore the universe.

Dr. Jacques Vallée has many scientific degrees, is a best-selling author and is regarded as one of the internet's founding fathers. But he is best renowned for his groundbreaking work on the subject of UFOs, where his bold theories call into question our understanding of alien life.

The Aztecs built one of the world's most powerful and feared empires and they claimed that they were guided by a pantheon of more than a thousand gods who came to Earth from different parts of the universe. Could the incredible story of their rise to power and their sudden demise, reveal a history of extraterrestrial intervention in Mesoamerica?