New discoveries reveal why the world's most ambitious engineering projects were abandoned, unraveling the dark mysteries and bloody secrets of these strange ruins. This episode is a mashup of S02E06, ''Secrets of the Alien Shrine" and S02E08, "Sea Fortress of Doom''.

America is the home to strange and incredible engineering projects that now lie in ruins, and new discoveries reveal how they were built and why they were suddenly abandoned. There are cities that are now empty ghost towns, bridges that were never finished, and roads to nowhere. This episode is a mashup of segments from S01E01, "Nazi Ghost Town", S01E06, "The Tesla Conspiracy", and S01E03, "Phantoms Of Chernobyl".

A terrifying sea fortress, a highway in the Amazon that suddenly vanishes, and 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.

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 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.

A secret structure on a sinister mountain, an industrial compound swallowed by a forest, and a mysterious run in a sand dune are strange deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A secret Russian military base in the Gobi Desert, a strange complex in an American wasteland, and a relic high atop a mountain are mysterious deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

Traces of a Russian hole to hell in the Arctic, a military base in America's wild west, and a strange looming tower are mysterious, deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A mysterious American pyramid built out of Cold War paranoia, a haunted prison, and a cluster of structures in the Atlantic are mysterious deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A strange Cuban prison, an eerie escape route built for Armageddon, and an underwater marvel that changed history are mysterious deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

Go inside the abandoned city of Chernobyl to follow an investigation into the truth behind the nuclear meltdown there over 30 years ago. New evidence reveals that this accident may be one of the greatest sabotages in history.