A strange alien shrine on a mountain peak, a bridge built in the Alaskan wilderness, and an American castle with a dangerous secret are mysterious deserted engineering projects. New discoveries reveal how they were built and why they were abandoned.

An American ghost town in the Amazon jungle, a secret Nazi base, and a deadly concrete fortress 866 miles long are mysterious deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A terrifying sea fortress, a highway in the Amazon that suddenly vanishes, a mysterious structure in the shadow of the Statue of Liberty are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

Eerie ghost ships stranded in an alien desert, sinister ruins known as the Dragon's Teeth, and a ghostly complex with a bloody past are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A ghost ship thousands of miles away from where anyone expected, a bridge to nowhere in Florida's Hurricane Alley, and a haunting mountain complex with a bloody secret are deserted engineering projects. New discoveries reveal why they were abandoned.

An alien Nazi structure that changed history, a strange Soviet monolith known as the Tower of Death, and a concrete ocean giant are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

An entrance to the underworld in the American wild, a haunting Soviet underwater prison, and a strange complex of towers in a forest of ice are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A strange deserted city in America's heartland, an eerie gigantic wall deep in snowcapped mountains, and a mysterious top-secret Soviet facility are deserted engineering projects. New discoveries reveal how they were built & why they were abandoned.

A deserted town in Spain with a bloody past and a ghost fleet heading nowhere are homes to dark American secrets, and new discoveries reveal how they were built and why they were abandoned.

A haunted lighthouse on Lake Michigan, a town where everyone seems to have vanished at once, and a secret complex of tunnels beneath London are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

An eerie prison with a dark past that became the setting of an iconic Hollywood movie and alien monoliths on a strange and remote island are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

An alien Stonehenge with a sinister purpose, an eerie building filled with strange labyrinths, and an endless concrete track in the middle of nowhere are deserted engineering projects, and new discoveries reveal why they were abandoned.

The world's strangest ghost towns are home to dark secrets, creepy buildings, and eerie sights, and new discoveries reveal why they were abandoned.

On a strange island off the coast of Croatia, the mysterious ruins of a long-abandoned hideout look like they once belonged to a James Bond supervillain, and new discoveries reveal why it was built and why they were abandoned.

Six breathtaking images, six unfathomable mysteries: from a gigantic tsunami in the air that never hits land, to a secret underground base in China, to an image from space that may reveal the location of the Garden of Eden.

Weird barren rings in the Namib Desert, an island the size of Manhattan that vanishes without trace and a lost city in the heart of the Amazonian jungle. What on Earth? Investigates six more mysteries captured from space.