An enormous concrete box with bizarre circular openings looms on the coast of an island near mainland China; Experts investigate and uncover tunnels leading to an enormous underground complex that nearly triggered a nuclear war.

The haunting remains of an isolated ghost town high in the Colorado mountains suggest a once booming mining community left in devastation; experts uncover an inhospitable land of shattered dreams where fortune seekers chased the American dream. 

A derelict beachside resort along the Black Sea is constructed upon deception and deep connections to the criminal underworld; experts investigate and uncover dark secrets behind a sprawling holiday complex constructed by the Russian mafia.

A breathtaking stainless steel tower seems otherworldly and out of place in the remote mountain forests of Croatia; experts investigate and uncover a dark past of Nazi-led conflict and a monument to a desperate fight for survival. 

The ruins of a dreamlike Polish palace hide an astonishingly dark history that's shrouded in mystery to this day; experts investigate and uncover an ornate gothic structure that concealed a nightmare of Nazi experimentation. 

A war-torn Italian ghost town immortalized by a legendary Hollywood director blurs the lines between fiction and reality; experts investigate and uncover a forgotten landscape of ruins captured in a WWII documentary. 

A desert island adrift in the Gulf of Mexico contains a massive and marooned structure with a contagious past; experts investigate and uncover a desolate military fortress turned prison and plagued by a deadly disease.

A strange sea fortress that guards icy waters is home to a grim secret; experts investigate the mysteries at this eerie structure, which fought an invisible enemy far more deadly than ever imagined.

Long, dome-like structures camouflaged by a rural landscape conceal the remains of concrete vaults with a hidden history; experts investigate and uncover state-of-the-art bunkers built to conceal and protect a deadly nuclear secret. 

A collection of ramshackle structures with a mystical facade lie mysteriously deserted on the tropical island of Bali; experts investigate and uncover the ruins of a bizarre amusement park complex with a disastrous past.

Abandoned towers of a fearsome warrior civilization and a castle that was once a fairy-tale estate are now haunted ruins; experts investigate the secrets behind these desolate fortresses to uncover how they were built and why they were abandoned. This is a mashup of S05E03 "Haunting of Heartbreak Castle," S06E07 "Towers of Blood," and S07E05 "Factory of Death." 

The world's abandoned structures hold new evidence about the lives and deeds of history's greatest heroes and villains, and using the latest discoveries at these mysterious sites, experts count down the ten most significant. 

America's Wild West is home to abandoned ruins that attest to the strange, dark, and mysterious things that once happened here; experts investigate the secrets behind these desolate places to uncover how they were built and why they were abandoned. The segments of this special come from various episodes.  

An island paradise home to a desolate prison and an abandoned system of caves for a secret society 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 S05E08 "Curse of Satan's Catacombs," S07E03 "Secrets of Mafia Island," and S01E02 "Curse of Hell Island."