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.

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.

First seen from space, the Eye of the Sahara is a beautiful 25-mile structure, but how it formed remains a mystery. And are extraordinary clouds over an island in the Indian Ocean evidence of a terrifying new weather weapon?

NASA astronaut Mike Barratt describes photographing a strange ring in the ice on the world’s oldest and most mysterious lake from the International Space Station. More rings on Lake Baikal have been seen since, baffling scientists.

A possible smoke screen over North Korea worries military analysts while an amateur archaeologist makes an extraordinary discovery with a satellite image -- has this image revealed not one but two forgotten pyramids in Egypt?

Images of earth from space reveal an intimate portrait of human activity. Cities glow bright while the wilderness remains dark. Why then is the Australian outback, lit up like a series of vast cities?

Desperate signs from lost veterans in Vietnam captured by satellite. A fleet of massive ships stranded in the middle of a vast desert. Strange walls stretching vast distances across Northern California. Just what on earth are they?

Satellites discover American stealth technology deep inside China. An unidentified cloud swamps America’s skis. And something truly massive is lurking beneath Loch Ness. Just what on earth are they?

Satellites spot strange spiral markings in the remote African desert. A weird deadly black blob is threatening the Florida Keys. Something massive found deep beneath the ice of Antarctica. Just what on earth are they?

A satellite spots a set of huge arrows in the badlands of the American west. A blood red waterfall stains Antarctica’s snows. A plague of huge holes in the Siberian landscape. Just what on earth are they?

The face of Christ is found in a field in Hungary. A photo that claims to show who shot down a passenger jet in Ukraine. A sinister shape in the mountains of Afghanistan that leads investigators to a hidden genocide.