A Texas cemetery claims to hold the body of an alien; petroglyphs depict strange beings in Utah.

Could Hindu scripture's Garuda be a misinterpreted alien craft?

Jerusalem's Temple Mount; Islam's shrine at Mecca; the temple at Baalbek, Lebanon.

A church in France; locals in Peru believe UFO sightings are connected to lost gold; alien library.

Modern rituals could reflect attempts by early humans to emulate ancient alien visitors.

An ancient mountaintop fortress made with laser-like tools; temples harness cosmic energy.

Some scientists believe plagues and epidemics can be linked with extraterrestrial interventions.

Strange carvings in the Mayan city of Copan; the ancient Nazca people who altered their bodies.

Iron swords, gunpowder, and rockets: human innovation or otherworldly help?

Australia's Black Mountains; a dark forest at the base of Mount Fuji in Japan.

The founding fathers knowledge of aliens shows up in symbols, architecture and documents.

Mass suicides. Human sacrifices. Unholy rituals.

People consider whether ancient man's structures were built by humans alone or with visitors.

Extraterrestrial origins in earthly encounters with the undead.

Mankind's incredible tales of gods with extraordinary powers and their relation to aliens.

Why are humans so different from every other species on Earth?