Throughout the ancient world, there are depictions of mysterious figures that appear to be half human and half bird. In many cultures, they are revered as divine and have magical abilities. But could these so-called "Birdmen" have truly existed? And if so, just what were they?

Zombies rising from their graves... Blood sucking vampires damned for all eternity... and humans trapped in a life and death struggle between heaven and hell. For thousands of years, mankind has told tales of encounters with strange, soulless creatures. Are these beliefs merely manmade fabrications - or could there be extraterrestrial origins in earthly encounters with the undead?

Luminous relics in the shape of human skulls. Otherworldly artifacts believed to harness the secrets of the universe. Are the Crystal Skulls part of an elaborate hoax? Or do they possess a great, perhaps even otherworldly power? The Crystal Skulls are some of the most controversial of ancient artifacts. While there have been literally hundreds of crystal skulls found throughout the world, according to legend, there are only thirteen which are believed to hold an awesome, mystical power whose secrets will be revealed when the skulls come together to form a global grid. Could this so-called "reunion of the skulls" awaken sacred knowledge of the gods? Knowledge that has been hidden from mankind for thousands of years? And if so, will the Crystal Skulls reveal the truth about our extraterrestrial past, or offer us a glimpse into our future?

Throughout the ancient world, structures were built to mirror the constellations in the night sky and this is only apparent when they are viewed from high above; a look at the possibility that these structures were designed as messages.

What is the meaning behind secret messages found throughout Washington, D.C.? Did America's Founding Fathers know something about ancient aliens that the general public did not? And if so, could this knowledge have been incorporated into the symbols, architecture, and even the founding documents of the United States of America?

Mass suicides. Human sacrifices. Unholy rituals. Throughout history, people have claimed to have otherworldly knowledge, and have led followers to commit horrific acts of violence. Are they con men? Are they insane? Or might the voices in their heads really be of an extraterrestrial origin? And if so, did they simply misinterpret the messages they received? Or might there be extraterrestrials with a sinister agenda?

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?

He is the evil one, the Prince of Darkness, the ruler of Hell. Satan conjures up horrifying images of a horned beast whose sole purpose is to destroy humanity. Yet there is evidence that the fallen angel we know as Satan may be misunderstood. New interpretations of ancient texts indicate that Satan may have been an extraterrestrial who was more of an ally to humanity than an enemy by passing along knowledge that planted the seed for civilization. Could Satan's reputation as the personification of evil be his punishment for leading early man out of darkness and ignorance? If so, might his evil acts really be expressions of revenge against the human creatures that abandoned him? Or are the devilish deeds associated with Satan part of a grand plan? A series of moral challenges intended to prepare us for our next, and perhaps final... close encounter?

The Reptilian alien is a fixture of science-fiction, from H.P. Lovecraft's tales of Valusians to the Cardassians in Star Trek, to the Visitors of the television series V. But could ancient myths about reptilian creatures provide evidence that they are more than just a pop-culture creation? Legends of serpent beings can be found on every continent. The Bible, the Quran and the ancient texts known as the Nag Hammadi codices all describe reptilian entities interacting with humans. In Mexico and Central America people worshiped the feather serpent god called Kukulkan or Quetzalcoatl. In India, the Nagas are half-human half-reptile gods who live underground in a place called Patala. And in China and Japan, many emperors claim to be the descendants of dragons. Could these stories represent real Reptilian beings that people all over the world actually encountered in the ancient past?

Ancient Aliens has followed investigators across the globe as they've gone directly to the sites where unexplained incidents have been reported. Now, Giorgio Tsoukalos takes a look back at the most extraordinary encounters that, as far as he's concerned, provide evidence of an extraterrestrial presence on Earth.

Ancient Aliens has examined the oldest and most mysterious rock art on Earth up close, and Giorgio Tsoukalos takes a look back at the incredible hieroglyphs, petroglyphs, and geoglyphs that he believes tell a worldwide story of alien visitation.

On every continent, there are stories of children who "stand out" for their strange abilities and advanced knowledge. They are said to have knowledge of things they shouldn't or couldn't know. The ancient Greeks, Egyptians and many other cultures have legends about exceptional children who are the offspring of humans and the gods. Could the stories be more than mere myth? Is it possible there are children being born on Earth today who can access their alien DNA--a connection that endows them with special gifts and the power to transform society?

Throughout history, spiritual leaders known as shamans have healed, protected and advised their people. But are they simply putting on elaborate ceremonies? Or could they be in contact with extraterrestrial realms? The Mongol army crushed their enemies and built a massive empire with the help of powerful shamans who could manipulate the weather. Amazonian shamans believe otherworldly beings taught them how to create a powerful brew that allows them to travel beyond Earth to gain knowledge. And on the desert plains of the Kalahari, the San Bushmen practice elaborate trance dances that unlock supernatural capabilities in their healers. Can shamans really communicate with otherworldly beings? Is it possible that through these spiritual mediators, extraterrestrials were able to influence mankind in the distant past? And could such celestial communication continue even today?

The Civil War nearly destroyed the great experiment known as the United States of America, but is it possible that the preservation of the republic was influenced by extraterrestrial beings? Abraham Lincoln described strange visions and premonitions that occur before pivotal moments in his presidency. Union officer Ambrose Bierce wrote about mysterious disappearances and inter-dimensional travel. And a ghostly image of George Washington was witnessed by hundreds of soldiers at Gettysburg–prompting an official government investigation. Is it possible that extraterrestrials were present during the Civil War? If so, were they simply passive observers, waiting to see if our fragile democracy could survive this test? Or did they take an active roll in order to preserve the Union?

Wondrous wizards... Mysterious sorcerers... And heavenly beings... possessed of unimaginable power. Throughout the ancient world, magic was used for everything from healing to communicating with the gods. But did magic really exist in the ancient times? Not as a form of theater--but as a means of replicating the power of the gods? Do ancient accounts of magic suggest evidence of advanced, otherworldly knowledge? A knowledge given to early humans as a means of helping them unlock their own - some might say "divine" - potential?

Mysterious surgeries performed by early humans... Strange beings with miraculous powers... And a cover up--destroying centuries of scientific knowledge. Are recent breakthroughs in medicine the result of years of research? Or does the knowledge of healing really come from an otherworldly source? Evidence of advanced medical procedures practiced in the ancient world has been found everywhere from carvings on the walls of temples to actual skeletal remains. But just who were the practitioners of this extraordinary science? And where did their knowledge of the human body come from? Accounts from various cultures describe similar divine, birdlike figures that brought advanced medical knowledge to mankind thousands of years ago. Who--or what--were these ancient surgeons? Is it possible that these Gods may have been extraterrestrial beings that came to Earth to teach humans how to heal themselves?

Powerful monarchs ruling by divine right. Centuries-old dynasties amassing enormous wealth. And legendary leaders wielding powerful weapons of mass destruction. Is it possible that ancient rulers were, in fact, connected with divine or, some would say, extraterrestrial forces? And, if so, what was their purpose? Ancient emperors, kings, and pharaohs were often attributed with otherworldly strength, ability, and wisdom; many were even considered gods by the people they ruled. Who were these exceptional leaders, and how did some accomplish so much in their time? Ancient Astronaut theorists believe that these great rulers throughout history were "chosen" and guided by extraterrestrials. Is it possible that the world's legendary leaders might have shared a common genetic trait? A so-called, "leadership gene"? And might this gene have been–not a product of genetic evolution–but inherited by mankind from some otherworldly source?

He is one of the most prolific inventors of the 20th century--and the man that actually electrified the world. Nikola Tesla shepherded mankind to a new industrial era and laid the groundwork for today's technological age--but could that have been by some otherworldly design? A man shrouded in mystery and intrigue, Tesla would speak about obtaining insights in a flash of genius, how he could visualize his inventions in full-detail and manipulate them in his mind, and his compulsion to invent the future. But he also claimed to have direct communication from 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?

Satellite images have revealed a giant face that appears to be carved into the Earth in Alberta, Canada, which has now become known far and wide as "The Badlands Guardian."

Divine substances were consumed by the gods but sometimes gifted to humans to impart great power or wisdom; could the food of the gods be sustenance for alien visitors and does it lend insight into humanity's future.

Accounts of creatures that can shape shift from one form into another can be found, but could similarities between the ancient stories and modern-day alien abduction accounts reveal that shape shifters are real and have come to Earth.

The team investigates the world's oldest and most incredible relics up close; Giorgio Tsoukalos takes a look back at the most mysterious artifacts from all over the globe, those he believes provide undeniable proof of extraterrestrial contact.

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?

They were the messengers of divine knowledge and seers who shared visions of the future. For thousands of years, human civilization has been guided by the words and deeds of ancient prophets, but just who--or what--were these prophets communicating with? Might the experiences of history's prophets be evidence of communication with a heavenly source--or were seers like Elijah and Joseph Smith actually communicating with extraterrestrial overlords? And if so, are there similar prophets at work today?

Sacred bones… Golden hats… And fragments of sacred objects thought to possess healing properties. All around the world, archaeologists have uncovered mysterious relics revered by ancient cultures for thousands of years. Now on display in museums, temples and churches, millions of people travel great distances just to be in their presence. What is it about these ancient objects that draws people to them? Could the truth of mankind's origins be found in the fabric, metal, stone and bones of our distant past? And could these mysterious relics really provide us with the ability to access divine or otherworldly power?