An infamous prison in the Amazon jungle and an underground labyrinth used by a secret police force contain a murderous past; experts investigate the secrets behind these hellish structures to uncover how they were built and why they were abandoned. This is a mashup of S05E06 "Secrets of the Doomsday Caves," S07E01 "Into the Murder Labyrinth," and S05E01 "Jungle of the Damned." 

Tunnels filled with human bones beneath the streets of Paris and ruins of a massive industrial operation contain a haunting past; experts investigate the evil secrets behind these deserted places to uncover how they were built and why they were abandoned. This is a mashup of S06E02 "Swamp of Despair," S04E04 "Labyrinth of the Dead," and S07E02 "American Ghost Park."

The haunting remnants of a backwoods Kentucky town and a deserted Spanish village with a bloody past are now abandoned ruins; experts investigate the mysteries of these deserted cities to uncover how they were built and why they were abandoned. This is a mashup of S03E06 "City of the Damned," S03E05 "America's Doomsday Town," and S07E06 "Ghosts of Black Mountain."

Desolate structures left in ghostly ruins are scattered across the US, and each holds a story waiting to be discovered; experts use cutting-edge tech to investigate these forgotten places and reveal how they were built and why they were abandoned. The segments of this special come from various episodes. 

A network of tunnels hiding a secret history of New York and a South African ghost town are now mysteriously abandoned ruins; experts investigate the cryptic secrets of these deserted places to uncover how they were built and why they were abandoned. This is a mashup of S05E04 "Kingdom of the Vanished," S03E08 "Nazi Death Star," and S03E01 "Doomsday at Dragon's Teeth."

An abandoned island complex and a haunted prison fortress contain a dark and terrifying past of bloodshed; experts investigate the violent secrets behind these ghostly structures to uncover how they were built and why they were abandoned. This episode is a mashup of S06E04 "Hell on Blood Island," S03E02 "Nightmare on Blood Mountain," and S05E07 "The Devil's Prison."

Evidence of an unspeakable evil in a set of Parisian buildings and an alien Stonehenge with a sinister purpose are now abandoned ruins; experts investigate the secrets of these dark structures to uncover how they were built and why they were abandoned. This episode is a mashup of S06E10 "House of Horror," S02E08 "Sea Fortress of Doom," and S03E10 "Secrets of Alien Stonehenge." 

A strange Soviet monolith, known as the Tower of Death, and a bizarre bunker constructed by a violent dictator are now forgotten ruins; experts investigate the secrets of these haunting structures to uncover how they were built and why they were abandoned. This episode is a mashup of S06E11 "Nightmare at Fort Paranoia," S04E05 "Treasure of Outlaw Valley," and S03E03 "Tower of Death."

The remains of a Scottish castle adapted into a WWII hospital and a classified complex on Lake Michigan are now forgotten ruins; experts investigate the secrets of these military facilities to uncover how they were built and why they were abandoned. This episode is a mashup of S07E11 "Ghosts of the Cursed Castle," S06E03 "End Times on Lake Michigan," and S06E07 "Towers of Blood."

The ruins of a mysterious hideout in Croatia and the decaying remains of Ireland's Alcatraz contain a haunting past; experts investigate the secrets behind these deserted island structures to uncover how they were built and why they were abandoned. This episode is a mashup of S07E10 "Mystery of the Alien Base," S04E02 "Secrets of Supervillain Island," and S06E09 "Anarchy on Ireland's Alcatraz." 

The remnants of a classified military wasteland and the ghostly remains of a remote Kentucky mining town are now forgotten ruins; experts investigate the secrets of these secluded facilities to uncover how they were built and why they were abandoned. This episode is a mashup of S07E05 "Factory of Death" and S07E06 "Ghosts of Black Mountain."

The desolate fortress of history's most infamous drug lord and a battle-scarred ruin in the Middle East contain a violent past; experts investigate the secrets of these mysterious compounds to uncover how they were built and why they were abandoned. This episode is a mashup of S07E09 "Fortress of the Spy," S04E08 "Pompeii's Gate to Hell," and S04E03 "Escobar's Castle."

The ruins of a historic Scottish castle are now a bewitching wilderness of hidden dangers with deadly booby traps obscured afoot; experts and historians reveal a bygone Second World War military hospital with bizarre ties to an infamous Nazi occupant.

A forgotten city in the cliffs of Colorado and a desolate complex of windowless buildings in the Rust Belt now stand in ruins; experts investigate the secrets of these deserted American mysteries to uncover how they were built and why they were abandoned. This episode is a mashup of S07E08 "Ruins of the Rust Belt," S05E06 "Secrets of the Doomsday Caves," and S04E07 "Alien Hell Portal."

Abandoned hangers and bunkers populate a bizarre facility in the middle of nowhere, but among them are other structures whose purpose are oddly obscured; experts investigate a highly-classified military cover-up with extraterrestrial objectives.

The decaying remains of a lost military base and the haunting remnants of a forgotten Nevada settlement are now barren wastelands; experts investigate the secrets behind these desert landscapes to uncover how they were built and why they were abandoned. This episode is a mashup of S07E07 "The Doom of El Dorado," S05E05 "Journey to Outcast Island," and S02E03 "Arctic Hell Pit."

A battle-scarred ruin in the Middle East is evidence of espionage that resulted in tremendous violence on a vast scale; experts expose the truth behind the strange building that holds the secrets of one of the world's most infamous deceptions.

A desolate fortress in a secluded mountainside and the remnants of a town in the backwoods of Kentucky are now ghostly ruins; experts investigate the secrets of these remote, rural mysteries to uncover how they were built and why they were abandoned. This episode is a mashup of S07E06 "Ghosts of Black Mountain," S06E08 "The Thing of Hell Mountain," and S04E09 "Haunting on Plague Island."

A complex of tall, windowless buildings in the American Rust Belt holds the secrets to a lost empire of industry and wealth; experts investigate these mysterious structures to reveal why this once powerful metropolis is now home to abandoned ruins.

An infamous prison in the Amazon and a deserted military facility in the remote English countryside contain a haunting and deadly past; experts investigate the secrets of these remarkable places to uncover how they were built and why they were abandoned. This episode is a mashup of S07E05 "Factory of Death," S05E01 "Jungle of the Damned," and S03E07 "The Town That Disappeared."

The haunting remnants of a settlement in the Nevada desert lie scattered with decaying machinery and remain trapped in a bizarre time-warp; experts uncover a forgotten mine where dreams of discovering a fortune were met with chaos and murder. A abandoned fortress on the cliffs of Malta that appears to be a prison at first glance mark the abandoned Fort Delimara. A abandoned facility that had the worlds tallest structure at the time of construction in Poland. A abandoned fortress that guarded the entrance to the Firth Of Fourth in Scotland during world war 1 and 2 is explored.

Forgotten places once home to Hollywood films and a terrifying prison fortress are now neglected and haunted ruins; experts investigate their mysteries and reveal the remarkable secrets behind the most iconic and ghostly places. This episode is a mashup of S07E04 "The World's Greatest Icons" and S05E07 "The Devil's Prison."

Ghostly remnants of a beautifully constructed town in the remote backwoods of Kentucky suggests a forgotten tale of utter catastrophe and devastation; experts investigate and uncover the dark and oppressive history of a deadly industrial mining complex. 

A Mediterranean island paradise and a once-thriving South African community are now all mysteriously deserted and desolate landscapes; experts investigate the secrets of these remarkable places to uncover how they were built and why they were abandoned. This episode is a mashup of S07E03 "Secrets of Mafia Island," S05E03 "Haunting of Heartbreak Castle," and S05E04 "Kingdom of the Vanished."

A deserted facility in the remote countryside features mysterious graffiti that may be highly advanced mathematical equations pointing to a dark secret; experts investigate this classified military wasteland with a deadly past. 

A deserted amusement park and ruins of a top-secret military doomsday bunker hold secrets to a strange and forgotten past; experts investigate these remarkable feats of engineering to uncover how they were constructed and why they were abandoned.

Places that were once home to or inspired Hollywood films, world-famous musicians, a sports legion, and war heroes are now run-down, abandoned, and forbidden; experts investigate their mysteries and reveal the astonishing secrets behind ten of the world's most iconic abandoned places.

Underground bunkers and subterranean labyrinths entomb dark secrets of the past waiting to be discovered; experts investigate the mysteries of these astonishing feats of engineering to uncover how they were constructed and why they were abandoned.

From secluded islands to cities perched along cliffs, abandoned structures, and failed engineering projects can be found in the world's most remote locations; using cutting-edge tech, experts reveal how they were built and why they were abandoned. This two-hour episode uses segments from various past episodes.

Some of the world's most nightmarish places are abandoned buildings and failed engineering projects; and using cutting-edge tech, experts make new discoveries to reveal the secrets of how they were built and why they were abandoned. This two-hour episode uses segments from various past episodes with cold weather as a common trait.

A Mediterranean island paradise is not all that it seems; its complex of abandoned buildings were once prisons for the world's most dangerous Mafiosi; experts investigate new evidence to reveal who was imprisoned here and the secrets they left behind.

Deep in the wilderness of the American south, a long-abandoned amusement park is home to secrets of a forgotten, imaginary world. When experts investigate, they reveal why this bizarre place was built and what caused its downfall.

An underground labyrinth once used by a secret police force could warp the mind and turn friend into foe; experts turn up new evidence pointing to madness, murder, and mayhem, revealing what happened in these cursed tunnels and why it was abandoned.