Experts follow evidence of a Nazi base in the Amazons to a dark discovery.

Images reveal an alien substance in the land of the Aztecs.

New evidence reveals a Viking portal to their spiritual realm.

Images reveal a forgotten war-torn fortress in the swamplands of Louisiana.

Experts uncover a gravesite with the remains of possible vampire burials.

A mystery in Hawaii points to human sacrifice and a shape-shifting god.

Satellites lead experts to an island that may be linked to a massacre.

When experts spot what appears to be an abandoned city in the Caspian Sea, they investigate declassified Cold War evidence to reveal an Atlantis-like city built by the Soviets; what they find exposes its long-lost secrets.

Satellites capture evidence of catastrophic and secret military testing.