The History Channel

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?

Across the globe, archaeologists have uncovered ancient tombs filled with strange items and writings. Remarkable similarities have been found at each of the sites. How is it possible that the burial chambers of distant cultures were so similar in design? Ancient Astronaut theorists believe that some of these complicated and technically advanced tombs were designed with the help of extraterrestrials.

Throughout the world, ancient rites and rituals are believed to connect humans to another dimension. But just who--or what--are we communicating with? Could today's rituals, such as festivals, coronations and funerals, be based on early man's attempts to emulate ancient alien visitors? If so, what other ancient rituals might find their roots in a kingdom--not of this world?

Ancient underwater cities can be found around the globe, but could these aquatic worlds be the ruins of unknown civilizations--or even proof of extraterrestrial visitations? The infamous tale of the long lost city of Atlantis may be a preserved memory of an ancient alien metropolis. Beneath Lake Titicaca in Peru, the ruins of recently discovered temples support local legends of an underwater UFO base. Ancient Indian texts, known as Sangams, describe sunken cities where aliens and humans intermingled thousands of years ago. Who could have built the 600-foot stepped stone structure off the coast of Japan--a site that may predate the Egyptian pyramids by thousands of years? Could evidence of ancient alien contact lie buried in Earth's deepest oceans?

Humans have always been fascinated with the one part of the world that we could not conquer--the sky. How did the earth's first flying creatures come to be? Examine the first vertebrate flyer, the pterosaur, which took to the air over 220 million years ago and eventually evolved to be the size of small airplanes. Scientists have long pondered how they, the largest flying creatures ever, were able to achieve such an astonishing feat. Scientists examine the fossil record compare pterosaurs to living birds to try and unlock how some species evolved to have the remarkable trait of flight.

How has our ability to communicate defined us as a species? Sharing information with each other has allowed humans to rise to the top of the food chain and dominate our environments. But humans aren't the only species that can communicate. Organisms as simple as bacteria can communicate, a strategy that lets them cooperate to take down creatures millions of times their own size. Fish use pheromones to warn each other about predators and find mates. Chemicals are also an effective means of communicating on land, and they've allowed insects--some of nature's smallest and most unassuming animals--to become the most populous and prolific on earth. The ability to interact stretches back billions of years and has often been one of the primary factors in a species ability to evolve and survive.

The story behind the world's most renowned modern myth. Enter creator J.R.R. Tolkien's fantastical world of hobbits, orcs and wizards, and uncover the real life influences that shaped his epic fantasy, The Lord of the Rings.

Idolized in ancient Norse mythology as the protector god, Thor battles evil ogres and a giant serpent bent on destroying mankind. It's the quintessential fight for survival that culminates in a final showdown between good and evil. But was the rise and fall of the hero Thor ancient code for something greater? Today, new discoveries unlock the hidden truth behind the Norse god of Thunder.

The tale of the strongest superhero in Greek mythology and his quest for redemption. To atone for committing a heinous crime, Hercules embarks on a series of impossible challenges known as the 12 Labors. Hercules endures as one of history's most influential demi-Gods, but recent archaeological discoveries suggest that mythology's strongest man may have been inspired by a real person.

In Greek mythology, ancient Greece's most powerful god wages an epic struggle against his father for control of the universe. It's the ultimate power struggle as the Olympians challenge the Titans in mythology's greatest showdown. This is a pivotal battle that experts believe may have been ancient code for a real world event--one of the greatest natural disasters the Earth ever experienced.

In 1945, at the end of a devastating global war, America emerged as a superpower. The Cold War presented the nation with a new and unprecedented crisis: the threat of nuclear annihilation. Instinctively, the country looked to the President to keep them safe during these dangerous times. The struggle against the spread of communism abroad, and the corrosive effects of inequality at home, demanded a new resolve and a steadfast international leader.

Since the mid 1960s, the power of the presidency has risen and fallen. It's been burdened by the personal failings of the men who occupied the office; by a Congress determined to reassert its power; by a skeptical and fragmented media; and by a public that had grown indifferent to politics. The Cold War ended, but global terror networks rose to present a more complicated threat. Despite these new challenges, the power of the office has grown substantially since it was first imagined--remaining the shining symbol of America's noble experiment in democracy.

This was the first time the English settlers engaged in the slaughter of Native Americans after years of relatively peaceful coexistence. Known as the Pequot War, this massacre in Mystic, Connecticut, set the pattern of possessing Indian land throughout the country.

Informational programming.

Informational programming.

Informational programming.

Informational programming.

The discovery of gold spurred tremendous financial and physical growth throughout the West. For the first time in history, individuals--not kings or sultans--could have gold for the taking, inspiring tens of thousands of people to make the arduous journey West.

Humans have always been fascinated with the one part of the world that we could not conquer--the sky. How did the earth's first flying creatures come to be? Examine the first vertebrate flyer, the pterosaur, which took to the air over 220 million years ago and eventually evolved to be the size of small airplanes. Scientists have long pondered how they, the largest flying creatures ever, were able to achieve such an astonishing feat. Scientists examine the fossil record compare pterosaurs to living birds to try and unlock how some species evolved to have the remarkable trait of flight.

How has our ability to communicate defined us as a species? Sharing information with each other has allowed humans to rise to the top of the food chain and dominate our environments. But humans aren't the only species that can communicate. Organisms as simple as bacteria can communicate, a strategy that lets them cooperate to take down creatures millions of times their own size. Fish use pheromones to warn each other about predators and find mates. Chemicals are also an effective means of communicating on land, and they've allowed insects--some of nature's smallest and most unassuming animals--to become the most populous and prolific on earth. The ability to interact stretches back billions of years and has often been one of the primary factors in a species ability to evolve and survive.

The story behind the world's most renowned modern myth. Enter creator J.R.R. Tolkien's fantastical world of hobbits, orcs and wizards, and uncover the real life influences that shaped his epic fantasy, The Lord of the Rings.

Idolized in ancient Norse mythology as the protector god, Thor battles evil ogres and a giant serpent bent on destroying mankind. It's the quintessential fight for survival that culminates in a final showdown between good and evil. But was the rise and fall of the hero Thor ancient code for something greater? Today, new discoveries unlock the hidden truth behind the Norse god of Thunder.

The tale of the strongest superhero in Greek mythology and his quest for redemption. To atone for committing a heinous crime, Hercules embarks on a series of impossible challenges known as the 12 Labors. Hercules endures as one of history's most influential demi-Gods, but recent archaeological discoveries suggest that mythology's strongest man may have been inspired by a real person.