We explore Fort Sherman, a jungle stronghold in Panama built to defend a prized American possession that soon faced the threat of an elaborate Nazi conspiracy.

We explore Fort Amador, the site of an American invasion in Panama, and a grisly Polish facility that once caged members of a revolutionary movement.

We head to the Tunisian desert to explore a vast chain of ruins that once stood in the way of Allied Victory - until a band of rogue heroes uncovered their weakness.

Exploring Seodaemun Prison, a facility in Seoul that helped spawn a legend known as South Korea's Joan of Arc.

An iron monster lost in the Alaskan tundra, a Crusader fort thrown into a modern conflict, and a prison built to house a mafia kingpin.

A little-known dark past explains the vast monolithic structures that dominate the small British island of Guernsey.

We explore Namibia's arid Skeleton Coast, where traces of a brutal but once vital industry lie scattered.

We visit the decaying remains of Old Essex County Jail in New Jersey, a facility that became a powder keg of injustice that was set to explode.

An engineering masterpiece carved into the cliff-face, and a long-range beacon that transmitted one of the most infamous messages in American history.

A real-life concrete jungle in America's 'Rust Belt', and an industrial facility that brought energy to a remote corner of the world.

In North Wales a secret facility which once manufactured mustard gas and enriched uranium lies in ruins. In Malta is a luxurious quarantine facility, that hides a dark secret.

We visit the Polish city of Walbrzych, where a fairytale castle on a cliff conceals a vast subterranean tunnel network linked to a legend of lost Nazi gold.

A fairy-tale castle that staged one of the strangest stories of the Second World War and a haunting complex on an old American Frontier.

Exploring the ruined site of Troy, that helped decode one of the world's most enduring mysteries.

Exploring Anchieta, a tropical island complex in Brazil and the scene of a dramatic uprising.

An American desert canyon where fortunes were made and lives were lost, and an island fortress in Scotland with an Achilles heel.

Learn about the strange-looking, derelict military facilities in Farnborough, which were once wind tunnels that played a vital role in WWII.

Exploring an Oklahoman town so wealthy it inspired a Hollywood film.

Exploring Agdam, a city in Azerbaijan raised to the ground in a conflict decided by a new weapon of war.

Exploring Old Joliet Prison, a battered facility near Chicago that descended into open war, but then hosted the Blues Brothers!

A Middle Eastern region littered with ruins and a strange facility in Taiwan that struck fear into the hearts of those who knew its true purpose.

An extended special featuring a deserted Caribbean city, an American ghost town still burning and an Arctic settlement facing a terrifying future.

Including an exploration of forgotten relics from the defence of America's homeland, at Fort Jackson, USA, concealed by the banks of the Mississippi River; a concrete behemoth at Lorient Sub Base, on the coast of France, that proved invulnerable to enemy bombardment; and a ghostly ruin at Gwrych that is now home to a haunting presence.

The Canfranc Railway Station is an elaborate abandoned Nazi railway station built near a town of only 500 people in the Pyrenees in Spain. But why was it built there and what secrets does it hold? Also examined in this episode is the Salton Sea Navy Base in California - a military post in the middle of the desert in the American west, the Kola Superdeep borehole - a wrecked record-holding Arctic facility in Russia that goes deep, deep underground, and a huge tower looming over an industrial area in Belgium. All of these extraordinary places and objects were at the cutting edge of design and construction, but now they stand disused, sometimes contaminated and sometimes dangerous.

The programme looks at a mysterious group of rusting ships stranded in an arid desert, a monstrous defensive line on the snow-covered peaks of the Italian Alps, a ghostly collection of buildings, and the sunken remains of a unique vessel.

A settlement in Argentina destroyed by floods, a town in the US that has been erased, and a Soviet dream-town that turned into a nuclear nightmare.

An abandoned prison beneath the water, a tunnel in the heart of a mountain, concrete towers hidden in the woods and a rusting coastal relic.

This week, find out why Fordlandia Rubber Town, a symbol of the American dream first established by Henry Ford in the 1920s, is now left rotting in the Amazonian rainforest. Also, what secrets do the enormous monoliths scattered across a secret forest complex in Eastern Poland hold? And what secrets does a fortified corridor of death with a Cold war past stretching for miles across Hötensleben, Germany hold? And a bizarre structure in South Western France built to speed trade was once at the forefront of design, now lies disused and abandoned, but why?

Claustrophobic prison cells that contain a story worthy of international acclaim, and a vast mountainside complex that held the power to change the world.

An abandoned concrete wall... five strange deserted structures. A lost escape route from nuclear Armageddon... A submerged link to D-day... Once they were at the cutting edge of design and construction, now they lie disused, contaminated and dangerous. But who built them? And why were they abandoned?

Exploring derelict villas in Sicily that reveal the island's complicated history with the Mafia and an aristocratic mansion in Ireland embroiled in a bizarre terrorist plot.

The Tunnels of Gibraltar were a Second World War espionage base, hidden in the Rock of Gibraltar, which lay undiscovered for decades. At Atlas-1 Test Site, are the remains of an ingenious US Airforce project that continues to keep people safe.

The desert town that faced a disaster of biblical proportions. Plus, vast coastal ruins that reveal a past once wiped from history.

A devastated cliff-top ruin, an extraordinarily tall tower, a concrete structure stranded at sea and a heavy metal monster in a field all feature.

The underground base with the power to destroy a nation, the site linked with an attempt to kill a dictator, and an ancient world discovered in the American wilderness.

A pioneering complex marked by both glory and tragedy that's soon to be lost forever, and towering remains from an industrial age.

We explore Schindler's Ark in the Czech Republic, a secret refuge in Europe's killing fields, and a lost Amazonian paradise deep in the Brazilian rainforest.

Exploring Camp Hero in Long Island, and a salt mine in Poland.

Exploring Air Studios, on the Island of Montserrat, that became a mecca for rock legends. Also Tskaltubo, in Georgia, built to host a fearsome dictator.

Exploring a picturesque French castle, the ruins of a Kansas City hospital, an ancient Turkish city, and an island in Ireland that brought its inhabitants closer to God.

Exploring an industrial ruin in the Florida Everglades that once competed in the greatest race humankind has ever witnessed.

Exploring a British fort that became a bizzare zoo, a brutalist school for Communist top brass and a lost world hides secrets of a vanished people.

A sprawling Wild West ghost town sits peaceful and abandoned in Montana, USA, but is still haunted by tales of murder, corruption and buried treasure. Also, a cold, dark, underground mountain network that cost the lives of thousands... the crumbling ruins of an English industry that turned poison into profit... a peaceful village that was shattered by the terrors of war.

Exploring a military strong-hold in the Philippines, a facility that spawned an American sporting great, and an English relic that hosted a cinematic sensation.

Exploring a luxury resort in Argentina, a Greek palace above a Mexican city and a former hotel in Hawaii.

Features a ruined compound in Colombia which was once home to Pablo Escobar and alien-looking structures with no apparent purpose, isolated in an empty English marshland in Denge, near Dungeness in Kent. But how and why were they ever built at all, and why are they now left abandoned?

Exploring a ghost town in Colorado, the remnants of an industrial enterprise in Puerto Rico, and a remote village on Cyprus.

Exploring a jungle refuge concealing a story of royal deceit, nuclear bunkers infiltrated by outsiders, and a haunted hospital marked by scandal.

Exploring Old Byron Hot Springs in the Californian desert - a once glittering Hollywood hotspot, converted into a top-secret interrogation centre.

An eerie, empty country village which hides a sad secret, a mysterious tower battered by the elements and a disused railway deep beneath the streets of a city.

We aim for the stars and find out why unwanted battleship guns allow the United States to gain vital information about the borders of space. We ask how the shattered remains of a secret Nazi base became the first on the path to a new world, with the development of the ground-breaking V2 rocket. We explore a forgotten structure deep in the Arizona desert to ask if it is the true home of America's space programme. And we reveal the bizarre link between a discarded oil drum and a Cold War struggle to survive in zero gravity.

Soaring across some of the widest rivers and deepest valleys on the planet, bridges have always been at the cutting edge of engineering. We travel high into the mountains of the Colorado desert to find out why a hidden engineering masterpiece could disappear at any time. We ask why a stretch of overgrown concrete in a Czech reservoir is known as 'Hitler's bridge'. We find out how the highest bridge in the world collapsed in less than one minute. Finally, we uncover the story behind Cape Town's invisible bridge, which never carried a single vehicle.

Within a dense Polish woodland sits a forgotten complex with an explosive history. Also, grand coastal defences in Ghana reveal a tortured past.

Featuring Italian ruins immortalised by Hollywood, a crumbling Chilean city with two lives and a brutalist Scottish relic whose prayers went unanswered.

Exploring the remains of a pioneering industry town in Ohio, a once beautiful Croatian resort bombarded by enemy fire, and an otherworldly garden of Eden in Mexico.

Exploring two ornate buildings in Texas that were once at the heart of the Mexican Revolution and a top-secret facility outside Berlin, used by a ruthless dictator to escape justice.

Exploring a palatial ruin in Philadelphia built from the riches of an industrial golden age and a country palace in Poland, the scene of a honey-trap devised to ensnare Napoleon.

Exploring a concentration camp in the Czech Republic used for a publicity stunt to fool the world and a stark facility that once housed Oscar Wilde.

Exploring a nuclear-armed facility in Arkansas that served as America's last line of defence in the Cold War and an industrial relic in Wales that felt a young Winston Churchill's wrath.

What happened to an infamous pirate city in Jamaica? Also, a grim gulag in Croatia and a Louisiana plantation caught up in the aftermath of the American Civil War.

Empty buildings and infrastructures are full of the echoes of real people and vanished lives, leaving many questions unanswered and mysteries unsolved. We explore the worlds strangest engineering projects that created empty silent cities. We ask why a ruined cold war air base has become a no-go area and how a tiny Japanese mining island become the most over-crowded place on the planet. We find out if the street layout of the Soviet Union's model city become a matter of life or death for its population. And how did Nazi Germany create a huge mind control facility at a holiday resort?

A formerly luxurious and strategic mountain-top villa on the island of Rhodes in the Mediterranean that's been ravaged by acts of revenge by locals since 1955.

A juggernaut of Soviet engineering which was crucial to the international space race. Deserted Scottish coastal defences and a complex that's crucial to American history.

Exploring Castel Volturno in Campana in Italy, Colorado and HMP Shepton Mallet in Somerset.

A creepy collection of buildings, monuments hidden in a Parisian park and an eerie graveyard of discarded ships strewn along the banks of a mighty river.

A now silent site that played a pivotal role defending the U.S through the 20th century. Plus, a crumbling Italian fortress and a ghostly Ukrainian mansion.

Bizarrely-shaped huts in India, once home to global superstars, are now eerily quiet and neglected, and a shattered compound in Colombia linked to a criminal mastermind.

Exploring a beachside resort with ties to the Russian mafia, a windswept base hiding lifesaving technology, and a site in Iowa plagued by its past.

Exploring a derelict stadium in Lithuania that hosted an unlikely Cold War matchup and an industrial relic in England.

Exploring Serbia, Fort Pike in Louisiana, and a mountainside refuge in Georgia that was revealed to the world by an act of God.

An ominous tower in the forests of Croatia, a New York City complex that broke the mould, and a grand facility guarding the London riverbanks.

How Europe's most advanced power station became a film set. Plus, the structures made by scientific pioneer Nikola Tesla in his thwarted quest to prove the US with free electricity.

A secretive underground base that concealed the power to destroy nations, and a sprawling industrial relic clinging to the edge of an unforgiving waterfall.

Legendary film sets with surprising pasts and real locations that inspired Hollywood. Within these decaying structures are the echoes of history.

Exploring a decrepit Liberian landmark with American origins, a desolate town in Belgium and a pioneering scientific structure in Cleveland.

Exploring the Dew Drop Inn in New Orleans that dared to take on the authorities and paid the price and Belgica Fort, built to defend an unlikely treasure.

The graffitied remains of a correctional facility in Atlanta, USA with a controversial and unexpected past, forgotten remnants of fraud and fusion on the Western border of Argentina and a mysterious ancient complex built by a devoted Khmer King in the jungles of Cambodia.

Exploring Dover Commando Fortress in South East England, where traces of a top-secret Commando raid are still visible.

A vast snowcovered monster in the icy wilderness of southern Alaska, a ruined super structure that overshadows everything around it in and a landscape of confusing and surprising structures that once represented a bold statement of Spain's plans for the future. Plus, a long, winding formation that was once supposed to help defend Hitler's Third Reich. And in Budapest, Hungary, the stripped skeleton of an industrial relic lies rusting away.

Examining a ghost island once belonging to a secretive country on the fringes of Europe. Also, a haunting site in the UK with evidence of strange burial practices.