Red Alert: During the Cold War, strange lights and unidentified objects put governments around the world on red alert. Could extra-terrestrials have been responsible? (2 of 6).

Skunk Ape: Deep in the Everglades, Troy recruits an army of swampers to investigate reports of a possible beast - the Skunk Ape - probing his friend's home. (S2, ep 6).

Aliens And Evil Places: Experts investigate creepy places associated with death. Could otherworldly connections be responsible for strange disappearances and suicides? (S3, ep 10).

Aliens And America's Founding Fathers: Could the Founding Fathers have hidden secrets about ancient aliens in their documents, buildings and symbols? Experts investigate. (S3, ep 11).

Ride of the Ancient Rhino: In the Philippines, archaeologists discover the remains of an ancient rhinoceros. Elsewhere, a Brazilian island is infested with thousands of vipers. (S1, ep 5).

By Night & By Day: The story of a deadly war that intertwines Germany, Poland, Japan, Italy and Spain, and the remorseless development of weapons and bombers. (5 of 6).

Visit the fascinating Indian retreat where The Beatles meditated, explore a copycat Chinese city and check out a glass factory in Israel. (S1, ep 15).

Aliens And Evil Places: Experts investigate creepy places associated with death. Could otherworldly connections be responsible for strange disappearances and suicides? (S3, ep 10).

Aliens And America's Founding Fathers: Could the Founding Fathers have hidden secrets about ancient aliens in their documents, buildings and symbols? Experts investigate. (S3, ep 11).

Reliquary Box: A look at what is arguably the most intriguing item in Carl and Hamilton's collection: the 15th-century reliquary casket. Season finale. (S1, ep 5).

The Vikings: Comedian John Thomson and historian Janina Ramirez join Al to explore the truth about Vikings and how they were so successful in Britain.

America: From bustling ports and strategic forts, to cultural quirks and cathedrals of commerce, this episode tells the story of the US through 12 key sites. (S1, ep 9).

By Night & By Day: The story of a deadly war that intertwines Germany, Poland, Japan, Italy and Spain, and the remorseless development of weapons and bombers. (5 of 6).

Documentary lifting the lid on the story of Alfred Hagen and his expedition to discover and rescue The Swamp Ghost, a WWII B-17 Bomber that crashed in Papua New Guinea.

Travel to Abu Dhabi's incredible Masdar City, check out the Wieliczka Salt Mine in Poland and visit an Indian village where the houses don't have doors. (S1, ep 20).

Black Triangle: A look at some of the most widely witnessed UFO events ever, including large black triangular objects in the night sky regularly spotted in the 80s and 90s. (3 of 6).

The Museum of Natural History Heist: A trio risk it all to steal priceless jewels at the American Museum of Natural History, creeping 125 feet above the streets of Manhattan. (S1, ep 6).

The Head of the Snake: Posing as a drug dealer, undercover informant Tony Tait infiltrates the secret biker club to take down leader Sonny Barger and meth cook Kenny Owens. (S1, ep 7).

Ride of the Ancient Rhino: In the Philippines, archaeologists discover the remains of an ancient rhinoceros. Elsewhere, a Brazilian island is infested with thousands of vipers. (S1, ep 5).

The Georgians: Amanda learns the customs of a true society girl, while Dan makes his own animal intestine condom and discovers how many brothels existed in London at the time. (S1, ep 3).

Aliens And Evil Places: Experts investigate creepy places associated with death. Could otherworldly connections be responsible for strange disappearances and suicides? (S3, ep 10).

Aliens And America's Founding Fathers: Could the Founding Fathers have hidden secrets about ancient aliens in their documents, buildings and symbols? Experts investigate. (S3, ep 11).

The Vikings: Comedian John Thomson and historian Janina Ramirez join Al to explore the truth about Vikings and how they were so successful in Britain.

British Raj: An exploration of 10 sites that defined the power, wealth and brutality of the British Empire's rise and fall. (S1, ep 8).

Black Triangle: A look at some of the most widely witnessed UFO events ever, including large black triangular objects in the night sky regularly spotted in the 80s and 90s. (3 of 6).

Documentary lifting the lid on the story of Alfred Hagen and his expedition to discover and rescue The Swamp Ghost, a WWII B-17 Bomber that crashed in Papua New Guinea.

The Great Flood: Experts find evidence suggesting that ancient aliens saved humanity from great floods sent by the gods. Can we rely on extra-terrestrials to save us again? (S7, ep 8).

The Vanishings: Experts explore the disappearance of civilisations throughout time and across the globe. Could clues left in their wake point to an otherwordly explanation? (S7, ep 9).

Hidden Pyramids: Experts investigate ancient man's apparent obsession with building pyramids, and whether extra-terrestrials may have helped with their construction. (S7, ep 11).

Part Two: Follow the course of the invasion as Strongbow wins victory after victory, while Henry II arrives to take control of Ireland and grants land to settlers from Britain. (2 of 2).

High Tech Surveillance: In the spy game, listening, learning and gaining the ability to eavesdrop requires ingenuity.

The Wild Unknown: The wild is a rich setting for myths and legends, with countless tales about the wilderness and the fearsome monsters within it. (S1, ep 2).

The Great Flood: Experts find evidence suggesting that ancient aliens saved humanity from great floods sent by the gods. Can we rely on extra-terrestrials to save us again? (S7, ep 8).

The Vanishings: Experts explore the disappearance of civilisations throughout time and across the globe. Could clues left in their wake point to an otherwordly explanation? (S7, ep 9).

Visit the plastic bottle village in Panama, discover floating boats in Greece, take a journey to Chernobyl and investigate the impact of the Centralia mine fire in Pennsylvania. (S1, ep 16).

Secret Weapon Sabotage: An elite force of Norwegian resistance fighters return to their invaded homeland to carry out a daring mission. (S1, ep 1).

Wat Tyler's Rebellion: After the Black Death, the lower class demand better wages - but England's involvements in the Hundred Year War has left the treasury empty. (S1, ep 1).

If You Wish For Peace, Prepare For War: Small arms production hit a boom in the early 1800s with the emergence of the modern cartridge; an invention that led to the lethal package. (1 of 3).

Now Available in Stores: Amidst financial troubles, Disney figure out how to bring their beloved characters off the screen and into the hands of millions through marketing. (S1, ep 4).

Battle of Hastings: Exploring the impact of the Battle of Hastings in 1066, Karl and Kevin continue their look at how weapons and body armour developed. (S1, ep 3).

A Family Secret: Armed with a mysterious map and unprecedented access to sacred Native American land, the Weibert family sets out to solve the mystery of Custer's lost gold. (S1, ep 1).

The Scientist: Galen of Pergamon makes a name for himself as a physician for gladiators. Meanwhile, a devastating plague sweeps through the city. (S1, ep 6).

The Lonely Hearts Killers: Despicable duo Raymond Fernandez and Martha Beck team up to con lonely women across the nation, posing as siblings to rob them of their riches. (S1, ep 3).

The Great Flood: Experts find evidence suggesting that ancient aliens saved humanity from great floods sent by the gods. Can we rely on extra-terrestrials to save us again? (S7, ep 8).

The Vanishings: Experts explore the disappearance of civilisations throughout time and across the globe. Could clues left in their wake point to an otherwordly explanation? (S7, ep 9).

Hidden Pyramids: Experts investigate ancient man's apparent obsession with building pyramids, and whether extra-terrestrials may have helped with their construction. (S7, ep 11).

Medusa: Medusa is the most infamous female fiend in Greek mythology - whose look turned every living thing to stone. But what is the true story behind the myth? (S1, ep 4).

Nazi She-Devil: Explore how women were active, often violent participants in the war and its atrocities - especially during the holocaust. (S1, ep 2).

Arthur of Brittany: The Boy Who Should Have Been King: Explore the tale of the teenage Duke of Brittany and would-be King of England's suspicious demise. (S1, ep 3).

Prince George: Tragedy or Treason: Explore the mystery surrounding Prince George's death in 1942 - does the royal family's ambivalence prove that his death was no accident? (S1, ep 3).

The Alien Agenda: Ancient alien theorists investigate evidence suggesting that extraterrestrials have played a pivotal role in the progress of mankind. (S7, ep 12).

Aliens And Robots: Experts investigate ancient tales and accounts of robots. If these sophisticated machines did exist in bygone days, what might have happened to them? (S8, ep 1).

Aliens B.C: Experts investigate whether the stories of a time when gods and otherworldly beings inhabited the planet are more than mere mythology. (S8, ep 2).

Finding the Center: From flat earth legends to Galileo's telescope, explore the major changes in humans' scientific understanding of planet Earth throughout history. (S1, ep 2).

Deadly Poisons: For some covert missions, assassination is the goal, and lethal toxins are deployed by spy agencies to kill perceived foes.

The Museum of Natural History Heist: A trio risk it all to steal priceless jewels at the American Museum of Natural History, creeping 125 feet above the streets of Manhattan. (S1, ep 6).

Visit a remarkable prison in South Korea, check out Bangkok's Ghost Tower and get to know the bicep-bulging men at Iceland's Jakabol Gym. (S1, ep 18).

Investigate the secrets behind the Hadzabe Myth in Tanzania, visit Colorado's incredible Cheyenne Mountain Complex and check out a fascinating abandoned boat in Croatia. (S1, ep 19).

Travel to Abu Dhabi's incredible Masdar City, check out the Wieliczka Salt Mine in Poland and visit an Indian village where the houses don't have doors. (S1, ep 20).

The Alien Agenda: Ancient alien theorists investigate evidence suggesting that extraterrestrials have played a pivotal role in the progress of mankind. (S7, ep 12).

Aliens And Robots: Experts investigate ancient tales and accounts of robots. If these sophisticated machines did exist in bygone days, what might have happened to them? (S8, ep 1).

Halfway through its fourth full year, the fortunes of war were running increasingly in favour of the Allies. The bombing of Hamburg and the Allied Tehran Conference take place. (S1, ep 6).

Tikal: Discover Tikal, one of the largest and most powerful archaeological sites and urban centers of pre-Columbian Mayan civilisation. (S3, ep 3).

Le Louvre: A look at the world's largest art museum, located in Paris, France and the home of the Mona Lisa.

Aliens B.C: Experts investigate whether the stories of a time when gods and otherworldly beings inhabited the planet are more than mere mythology. (S8, ep 2).

War: The violent story of Romulus and Remus, the brutal Vikings and the Valkyries, the Trojan War and exploring the influence of Homer's Iliad on Alexander the Great. (S1, ep 3).

Fame: Explore a collection of figures and groups who have redefined the notion of fame through history, from royal families across the globe to Marilyn Monroe and The Beatles. (S1, ep 6).

The Alien Agenda: Ancient alien theorists investigate evidence suggesting that extraterrestrials have played a pivotal role in the progress of mankind. (S7, ep 12).

Aliens And Robots: Experts investigate ancient tales and accounts of robots. If these sophisticated machines did exist in bygone days, what might have happened to them? (S8, ep 1).

Aliens B.C: Experts investigate whether the stories of a time when gods and otherworldly beings inhabited the planet are more than mere mythology. (S8, ep 2).

The Scientist: Galen of Pergamon makes a name for himself as a physician for gladiators. Meanwhile, a devastating plague sweeps through the city. (S1, ep 6).

The Tudor Tower: A new recruit joins the team and begins his career as a Beefeater with some testing exams. The Chief Curator reveals the history of Anne Boleyn within the walls. (2 of 4).

Amy Dudley: The Queen, Her Lover and His Wife: The death of Robert Dudley's wife in 1560 caused a scandal - as the nobleman was Elizabeth I's alleged lover. (S1, ep 4).

Ludwig II: The Mad King of Bavaria: Explore the controversy surrounding the death of the eccentric King Ludwig, whose unstable behaviour saw him deposed. (S1, ep 4).

Aliens And The Creation Of Man: Experts investigate the mysterious Creation of Man, asking whether unexplained advances in human evolution could have been down to aliens. (S3, ep 12).

Alien Messages: Could some of our ancient texts and structures be home to secret messages left by alien ancestors? If so, what can we learn from them? (S1, ep 6).

Pohnpei's Ancient City: In the northwestern Pacific, a tourist stumbles across a mysterious structure. Elsewhere, an unsettling sight is revealed on the island of New Guinea. (S1, ep 6).

Terror of the World: The story of a deadly war that intertwines Germany, Poland, Japan, Italy and Spain, and the remorseless development of weapons and bombers. (6 of 6).

Visit the plastic bottle village in Panama, discover floating boats in Greece, take a journey to Chernobyl and investigate the impact of the Centralia mine fire in Pennsylvania. (S1, ep 16).

Aliens And The Creation Of Man: Experts investigate the mysterious Creation of Man, asking whether unexplained advances in human evolution could have been down to aliens. (S3, ep 12).

Alien Messages: Could some of our ancient texts and structures be home to secret messages left by alien ancestors? If so, what can we learn from them? (S1, ep 6).

Belief and Superstition: Science reveals new insights into belief and superstition in the land of the Pharaohs, from finding the long-lost 'Land of Punt' to Tutankhamun. (S1, ep 1).

Win Every War. Scotland vs England: Al is joined by Sanjeev Kohli as they visit Craufurdland Castle to explore the truth behind famous battles from the Wars of Scottish Independence.

Japan: Travel through time to explore the past 1500 years of one of the world's most unique and diverse ancient cultures - Japan. (S1, ep 10).

Terror of the World: The story of a deadly war that intertwines Germany, Poland, Japan, Italy and Spain, and the remorseless development of weapons and bombers. (6 of 6).

The Disappeared: New theories shed light on the world's biggest mysteries, including the unsolved disappearances of aviator Amelia Earhart and hijacker DB Cooper. (S1, ep 1).

Grand Canyon National Park: A strange series of events in Grand Canyon National Park leads researchers to speculate whether its power comes from forces that cannot be explained. (S1, ep 1).

Everglades National Park: A plane crash in the Everglades National Park leads to strange hauntings - and some believe the park may exert a dark, transformative power. (S1, ep 2).

UFOs Crash Sites: Alien autopsies and recovered pieces of an extra-terrestrial spacecraft: this is the story of the Roswell incident and the truth behind the UFO. (4 of 6).

God's Holy Warriors: Did our ancestors believe they were cursed? Professor Alice Roberts explores historic cataclysmic events such as wars and floods to dispel the myths. (4 of 5).

The Mary Rose: Ross returns to training with dive master Neil Brock and explores the site of Britain's most famous wreck: the Mary Rose. (S1, ep 1).

Pohnpei's Ancient City: In the northwestern Pacific, a tourist stumbles across a mysterious structure. Elsewhere, an unsettling sight is revealed on the island of New Guinea. (S1, ep 6).

Henning Franzmeier and his team of archaeologists undertake excavations in Pi-Ramses, hoping to discover the truth about the ancient Egyptian pharaoh Ramses II's lost city. (1 of 2).

Aliens And The Creation Of Man: Experts investigate the mysterious Creation of Man, asking whether unexplained advances in human evolution could have been down to aliens. (S3, ep 12).

Aliens And Deadly Cults: A look at cases where people have claimed strange voices urged them to commit horrific deeds. Could they have been obeying the orders of aliens? (S3, ep 13).

Win Every War. Scotland vs England: Al is joined by Sanjeev Kohli as they visit Craufurdland Castle to explore the truth behind famous battles from the Wars of Scottish Independence.

America: From bustling ports and strategic forts, to cultural quirks and cathedrals of commerce, this episode tells the story of the US through 12 key sites. (S1, ep 9).

UFOs Crash Sites: Alien autopsies and recovered pieces of an extra-terrestrial spacecraft: this is the story of the Roswell incident and the truth behind the UFO. (4 of 6).

The Disappeared: New theories shed light on the world's biggest mysteries, including the unsolved disappearances of aviator Amelia Earhart and hijacker DB Cooper. (S1, ep 1).

Aliens And The Secret Code: Experts scrutinise prehistoric ruins, asking whether humans could have built these advanced structures alone. Might they have had alien help? (S3, ep 14).

The Tesla Experiment. Giorgio A Tsoukalos draws on evidence from past series as he asks whether Nikola Tesla was communicating with extraterrestrials. (S1, ep 3).

Creature of Lake Eacham: A mysterious creature that glows in the dark is discovered in the Australian rainforest. Hundreds of human bones are found in a Belizean cave. (S1, ep 7).

If You Wish For Peace, Prepare For War: Small arms production hit a boom in the early 1800s with the emergence of the modern cartridge; an invention that led to the lethal package. (1 of 3).

Check out the Chinese railway that runs through residential buildings, take a tour of a mysterious forest in Poland and explore amazing underground locations around the world. (S1, ep 17).

Aliens And The Secret Code: Experts scrutinise prehistoric ruins, asking whether humans could have built these advanced structures alone. Might they have had alien help? (S3, ep 14).

The Tesla Experiment. Giorgio A Tsoukalos draws on evidence from past series as he asks whether Nikola Tesla was communicating with extraterrestrials. (S1, ep 3).

Egyptian Genius: Journey back in time to understand the brainpower behind Ancient Egypt's revolutionary breakthroughs in every field, from medicine to engineering. (S1, ep 2).

India: Al Murray is joined by legendary master of stand-up, Anuvab Pal, to explore the truth about Britain's rocky relationship with India. (S1, ep 1).

Ancient Greece (Part 1): Explore the great historic sites of the Minoan civilisation on Crete, Mycenae in the Peloponnese and the emerging Greek city states such as Corinth. (S2, ep 1).

If You Wish For Peace, Prepare For War: Small arms production hit a boom in the early 1800s with the emergence of the modern cartridge; an invention that led to the lethal package. (1 of 3).

Cover-Ups: What's going on in Area 51? What crashed at Roswell? And what's happening at the top-secret Dugway Proving Ground? Experts go in search of answers. (S1, ep 2).

Hawaii Volcanoes National Park: The Hawaii Volcanoes National Park is the site of strange events. Are they linked to the legendary Native Hawaiian Goddess of the Volcano, Pele? (S1, ep 3).

Joshua Tree National Park: Are UFO sightings at Joshua Tree linked to an anti-aging machine and a powerful creature called the Yucca Man? (S1, ep 4).

UFO's vs Airlines: Are UFOs a threat to civil aviation? The culture of silence within the aviation industry could speak volumes. (5 of 6).

South Africa: Al and local comedian Loyiso Gola embark on a road trip through the true British imperial history in South Africa. (S1, ep 3).

The Other Cleopatra: Cleopatra II's reign was a truly dramatic and grisly tale. She saw her dynasty torn apart by hatred - but also saved it from destruction. (S1, ep 2).

Creature of Lake Eacham: A mysterious creature that glows in the dark is discovered in the Australian rainforest. Hundreds of human bones are found in a Belizean cave. (S1, ep 7).

The Price of Loyalty: Hornigold's crew deposes him for his refusal to attack English ships, but one man remains loyal. Pirate raids on British slaves provokes outrage. (S1, ep 3).

Aliens And The Secret Code: Experts scrutinise prehistoric ruins, asking whether humans could have built these advanced structures alone. Might they have had alien help? (S3, ep 14).

Aliens And The Undead: Experts study previous reports of zombies, vampires and spirits. Could these sightings of the undead actually have been alien encounters? (S3, ep 15).

India: Al Murray is joined by legendary master of stand-up, Anuvab Pal, to explore the truth about Britain's rocky relationship with India. (S1, ep 1).

Japan: Travel through time to explore the past 1500 years of one of the world's most unique and diverse ancient cultures - Japan. (S1, ep 10).

UFO's vs Airlines: Are UFOs a threat to civil aviation? The culture of silence within the aviation industry could speak volumes. (5 of 6).

Cover-Ups: What's going on in Area 51? What crashed at Roswell? And what's happening at the top-secret Dugway Proving Ground? Experts go in search of answers. (S1, ep 2).

Aliens Gods And Heroes: Ancient alien theorists explore the origins of mythical gods. Could these tales of superhuman beings be based on sightings of extraterrestrials? (S3, ep 16).

The Mayan Conspiracy: Experts investigate startling evidence suggesting that the Ancient Maya conspired with aliens. Was this how they acquired their knowledge of astrology? (S4, ep 1).

Stone Secrets of Kilwa Island: A mysterious site with huge stone blocks is discovered off the coast of Tanzania. In the Guatemalan rainforest, hundreds of human bones are found. (S1, ep 8).

Rise of the Machines: While the single shot rifle remained a mainstay until WWI, machine guns had been in development since the final days of the American Civil War. (2 of 3).

Visit a remarkable prison in South Korea, check out Bangkok's Ghost Tower and get to know the bicep-bulging men at Iceland's Jakabol Gym. (S1, ep 18).

Aliens Gods And Heroes: Ancient alien theorists explore the origins of mythical gods. Could these tales of superhuman beings be based on sightings of extraterrestrials? (S3, ep 16).

The Mayan Conspiracy: Experts investigate startling evidence suggesting that the Ancient Maya conspired with aliens. Was this how they acquired their knowledge of astrology? (S4, ep 1).

Villainy and Vice: Science shines a light on the dark side of Ancient Egypt, from a 5,000-year-old homicide to drug-fuelled debauchery - and one very shocking revelation. (S1, ep 3).

Jamaica: Al is joined by Chris Daley to uncover the real story of the pirates of the Caribbean and the barbaric realities of the slave trade. (S1, ep 2).

Ancient Greece (Part 2): Venture back to ancient Greece and explore the great sites of Athens, Delphi, Olympia and Epidaurus which form some of the greatest sites in antiquity. (S2, ep 2).

Rise of the Machines: While the single shot rifle remained a mainstay until WWI, machine guns had been in development since the final days of the American Civil War. (2 of 3).

Paranormal Destinations: Experts investigate the US government's experiments into teleportation. They also dig into strange happenings at Mount Shasta and Skinwalker ranch. (S1, ep 3).

Glacier National Park: In Montana's Glacier National Park, some claim that there is a hidden underground Nazi base that may even have been the final hideout for Hitler himself. (S1, ep 5).

Mount Shasta National Forest: From inexplicable disappearances to mysterious experiments, events in Mount Shasta National Park may be explained by an ancient Karuk Indian legend. (S1, ep 6).

Shoot 'Em Down: Fighter pilots from the UK to Peru have encountered UFOs. What happens when a UFO gets too close for comfort? (6 of 6).

Breakout in Plain Sight: An Iranian-American psychopath goes to jail in Southern California, but escapes before he can be transferred to a higher security prison. (S2, ep 8).

Creating a New World: Against all odds, Disney turns 27,000 acres of muddy Florida swampland into the world's largest - and most visited - theme park. (S1, ep 5).

Stone Secrets of Kilwa Island: A mysterious site with huge stone blocks is discovered off the coast of Tanzania. In the Guatemalan rainforest, hundreds of human bones are found. (S1, ep 8).

Hades: Discover the myth of ancient Greece's most feared god. Hades takes us behind the veil of the ancient Greek belief in life after death with chilling tales. (S1, ep 2).

Aliens Gods And Heroes: Ancient alien theorists explore the origins of mythical gods. Could these tales of superhuman beings be based on sightings of extraterrestrials? (S3, ep 16).

The Mayan Conspiracy: Experts investigate startling evidence suggesting that the Ancient Maya conspired with aliens. Was this how they acquired their knowledge of astrology? (S4, ep 1).

Jamaica: Al is joined by Chris Daley to uncover the real story of the pirates of the Caribbean and the barbaric realities of the slave trade. (S1, ep 2).

Ancient Greece (Part 1): Explore the great historic sites of the Minoan civilisation on Crete, Mycenae in the Peloponnese and the emerging Greek city states such as Corinth. (S2, ep 1).

Shoot 'Em Down: Fighter pilots from the UK to Peru have encountered UFOs. What happens when a UFO gets too close for comfort? (6 of 6).

Paranormal Destinations: Experts investigate the US government's experiments into teleportation. They also dig into strange happenings at Mount Shasta and Skinwalker ranch. (S1, ep 3).

The Doomsday Prophecies: Experts scrutinise the Maya Calendar, which predicted the world would end in 2012. Could it have anticipated the arrival of an extraterrestrial god? (S4, ep 2).

The Greys: Experts investigate the 'greys' - mysterious beings with big heads and eyes found carved into rocks. Who are these strange figures and what inspired them? (S4, ep 3).

Secret Cave Of Kolombangara: A volcanic island called Kolombagara, with a secret cave, rises out of the Pacific Ocean. In Vietnam, bones from an unknown animal are found. (S1, ep 9).

The Gods of War: The industrial revolution changed it all when it came to cannons as they evolved from wholly inaccurate and immobile to deadly killing machines. (3 of 3).

Investigate the secrets behind the Hadzabe Myth in Tanzania, visit Colorado's incredible Cheyenne Mountain Complex and check out a fascinating abandoned boat in Croatia. (S1, ep 19).

The Doomsday Prophecies: Experts scrutinise the Maya Calendar, which predicted the world would end in 2012. Could it have anticipated the arrival of an extraterrestrial god? (S4, ep 2).

The Greys: Experts investigate the 'greys' - mysterious beings with big heads and eyes found carved into rocks. Who are these strange figures and what inspired them? (S4, ep 3).

Ancient Icons In The Modern Age: Explore the truth and lies behind ancient Egypt's best known and loved icons, including the Great Sphinx, Tutankhamun and more. (S1, ep 4).

South Africa: Al and local comedian Loyiso Gola embark on a road trip through the true British imperial history in South Africa. (S1, ep 3).

Dutch Golden Age (Part 1): Explore how the 80 Years' War left the Spanish Empire financially ruined, while the Dutch Republic - by contrast - became a global commercial power. (S2, ep 3).

The Gods of War: The industrial revolution changed it all when it came to cannons as they evolved from wholly inaccurate and immobile to deadly killing machines. (3 of 3).

Strange Triangles: Three places, three spooky stories. Experts examine weird sightings and unsolved disappearances at Bennington, Bermuda and Bridgewater triangles. (S1, ep 4).

El Yunque National Forest: Few know that one of the US's most mysterious National Parks is in Puerto Rico - a place some believe is home to a creature known as the Chupacabra. (S1, ep 7).

Gettysburg National Military Park: Many believe Gettysburg National Military Park is haunted by its violent past - here, explore some incredible claims about the park's history. (S1, ep 8).

The Doomsday Prophecies: Experts scrutinise the Maya Calendar, which predicted the world would end in 2012. Could it have anticipated the arrival of an extraterrestrial god? (S4, ep 2).

Into the Mountains (Tibet): Himmler's belief in the theory that the Himalayas were home to the Nazis' Aryan ancestors leads to an SS mission to the mountains. (S1, ep 4).

Haircut for a Mob Boss: Umberto 'Albert' Anastasia, once the chief of the notorious 'Murder Incorporated' crime firm, winds up the target of a mob hit in a barber shop chair. (S1, ep 4).

Secret Cave Of Kolombangara: A volcanic island called Kolombagara, with a secret cave, rises out of the Pacific Ocean. In Vietnam, bones from an unknown animal are found. (S1, ep 9).

Commodus: Just one of Rome's emperors is willing to step out of the Imperial Box into the arena and his name is Commodus, a man with a reputation for making enemies. (S1, ep 7).

The Doomsday Prophecies: Experts scrutinise the Maya Calendar, which predicted the world would end in 2012. Could it have anticipated the arrival of an extraterrestrial god? (S4, ep 2).

The Greys: Experts investigate the 'greys' - mysterious beings with big heads and eyes found carved into rocks. Who are these strange figures and what inspired them? (S4, ep 3).

South Africa: Al and local comedian Loyiso Gola embark on a road trip through the true British imperial history in South Africa. (S1, ep 3).

Ancient Greece (Part 2): Venture back to ancient Greece and explore the great sites of Athens, Delphi, Olympia and Epidaurus which form some of the greatest sites in antiquity. (S2, ep 2).

El Yunque National Forest: Few know that one of the US's most mysterious National Parks is in Puerto Rico - a place some believe is home to a creature known as the Chupacabra. (S1, ep 7).

Gettysburg National Military Park: Many believe Gettysburg National Military Park is haunted by its violent past - here, explore some incredible claims about the park's history. (S1, ep 8).

Strange Triangles: Three places, three spooky stories. Experts examine weird sightings and unsolved disappearances at Bennington, Bermuda and Bridgewater triangles. (S1, ep 4).

Aliens And Mega-Disasters: Did Mother Nature cause the volcanoes, earthquakes and floods of ancient times? Or could aliens have been responsible? Experts investigate. (S4, ep 4).

The Nasa Connection: Experts open up NASA and secret government files. Can they find proof of alien contact in the recent or ancient past? (S4, ep 5).

Mystery of Mexico's Skull Cave: A cave bursting with bones is found in the jungles of Mexico. In Hawaii, archaeologists find unusual sculptures with big heads and bulging eyes. (S1, ep 10).

Albert Speer: In his role as Adolf Hitler's favourite architect, Albert Speer was a central figure in the Fuhrer's inner circle and helped cement his position in power. (S1, ep 1).

Travel to Abu Dhabi's incredible Masdar City, check out the Wieliczka Salt Mine in Poland and visit an Indian village where the houses don't have doors. (S1, ep 20).

Aliens And Mega-Disasters: Did Mother Nature cause the volcanoes, earthquakes and floods of ancient times? Or could aliens have been responsible? Experts investigate. (S4, ep 4).

The Nasa Connection: Experts open up NASA and secret government files. Can they find proof of alien contact in the recent or ancient past? (S4, ep 5).

Health and Wealth: With the help of modern science, uncover the secrets of health and wealth in Ancient Egypt from Queen Hatshepsut's death to a case of breast cancer. (S1, ep 5).

Australia: Al and comic Kevin Kropinyeri reveal that Captain Cook was not really a Captain and explore the Aboriginal history of Australian cricket. (S1, ep 4).

Dutch Golden Age (Part 2): After the Dutch Republic declared its independence from Spain, it was cut off from the lucrative spice trades. Where did they go from here?. (S2, ep 4).

Albert Speer: In his role as Adolf Hitler's favourite architect, Albert Speer was a central figure in the Fuhrer's inner circle and helped cement his position in power. (S1, ep 1).

Unidentified: What did UFO chaser Captain Mantell see before he was killed? Plus, experts investigate a close encounter in Texas and a mysterious crash at Shag Harbour. (S1, ep 5).

Big Bend National Park: A series of incidents in Big Bend National Park leave experts convinced of secret alien activities taking place there. (S2, ep 1).

Death Valley National Park: Discover the forces living in the secret underworld of Death Valley National Park, where a series of deaths and disappearances have taken place. (S2, ep 2).

Aliens And Mega-Disasters: Did Mother Nature cause the volcanoes, earthquakes and floods of ancient times? Or could aliens have been responsible? Experts investigate. (S4, ep 4).

The Dunbar Armored Depot Heist: Allan Pace and five old pals plan and execute a daring robbery of Los Angeles based Dunbar Armored Car Company in 1997. (S1, ep 7).

Hell's Hitmen: The Hells Angels use hang-arounds and Angel wannabes to do their dirty work, with Ted Soke grooming his own son Donny to become a serial killer. (S1, ep 8).

Mystery of Mexico's Skull Cave: A cave bursting with bones is found in the jungles of Mexico. In Hawaii, archaeologists find unusual sculptures with big heads and bulging eyes. (S1, ep 10).

The Victorians: Amanda Holden and Dan Jones explore the Victorian era, one of the most sexually progressive societies in history, to learn more about the Queen's dirty secrets. (S1, ep 4).

Aliens And Mega-Disasters: Did Mother Nature cause the volcanoes, earthquakes and floods of ancient times? Or could aliens have been responsible? Experts investigate. (S4, ep 4).

The Nasa Connection: Experts open up NASA and secret government files. Can they find proof of alien contact in the recent or ancient past? (S4, ep 5).

Australia: Al and comic Kevin Kropinyeri reveal that Captain Cook was not really a Captain and explore the Aboriginal history of Australian cricket. (S1, ep 4).

Dutch Golden Age (Part 1): Explore how the 80 Years' War left the Spanish Empire financially ruined, while the Dutch Republic - by contrast - became a global commercial power. (S2, ep 3).

Big Bend National Park: A series of incidents in Big Bend National Park leave experts convinced of secret alien activities taking place there. (S2, ep 1).

Death Valley National Park: Discover the forces living in the secret underworld of Death Valley National Park, where a series of deaths and disappearances have taken place. (S2, ep 2).

Unidentified: What did UFO chaser Captain Mantell see before he was killed? Plus, experts investigate a close encounter in Texas and a mysterious crash at Shag Harbour. (S1, ep 5).

NASA's Secret Agenda: Experts investigate whether rocket scientist Wernher von Braun might have found inspiration in technology found at the alleged UFO crash in Roswell. (S8, ep 3).

Alien Evolution: A look at the accounts of modern-day alien abductees. Plus, could the bizarre Paracas skulls discovered by Julio Tello be of extraterrestrial origin? (S8, ep 5).

The Other Earth: Ancient Alien theorists explore world mythology as they investigate whether extraterrestrials could be responsible for our existence. (S8, ep 6).

Within a quiet valley lies a battlefield full of bones and weapons predating any previously discovered battleground. What experts unearth will rewrite our understanding of warfare. (1 of 2).

New. Special Ops and Saboteur: A look at some of the most famous missions in modern history. Special operations require skilful people, but elite technology plays a part too.

War: The violent story of Romulus and Remus, the brutal Vikings and the Valkyries, the Trojan War and exploring the influence of Homer's Iliad on Alexander the Great. (S1, ep 3).

NASA's Secret Agenda: Experts investigate whether rocket scientist Wernher von Braun might have found inspiration in technology found at the alleged UFO crash in Roswell. (S8, ep 3).

Alien Evolution: A look at the accounts of modern-day alien abductees. Plus, could the bizarre Paracas skulls discovered by Julio Tello be of extraterrestrial origin? (S8, ep 5).

The Disappeared: New theories shed light on the world's biggest mysteries, including the unsolved disappearances of aviator Amelia Earhart and hijacker DB Cooper. (S1, ep 1).

Churchill Strikes Back: December 1941: Under cover of a fierce naval bombardment, a taskforce of elite British commandos sail towards the Norwegian town of South Vaagso. (S1, ep 4).

Boudica's Revolt: From the outset of the Roman conquest of Britannia, the flame of rebellion is smouldering - and with the death of the Iceni King, peace will be shattered. (S1, ep 2).

Rise of the Machines: While the single shot rifle remained a mainstay until WWI, machine guns had been in development since the final days of the American Civil War. (2 of 3).

Creating a New World: Against all odds, Disney turns 27,000 acres of muddy Florida swampland into the world's largest - and most visited - theme park. (S1, ep 5).

The Great War - the Somme: Presenter Karl Ude-Martinez takes a tour of the weapons used during the Battle of the Somme in 1916, including machine guns and poison gas. (S1, ep 4).

Writings on the Wall: In Montana, Penny and Craig close in on the priceless cache of weapons stripped from Custer's soldiers after the Battle of the Little Big Horn. (S1, ep 2).

Commodus: Just one of Rome's emperors is willing to step out of the Imperial Box into the arena and his name is Commodus, a man with a reputation for making enemies. (S1, ep 7).

Haircut for a Mob Boss: Umberto 'Albert' Anastasia, once the chief of the notorious 'Murder Incorporated' crime firm, winds up the target of a mob hit in a barber shop chair. (S1, ep 4).

NASA's Secret Agenda: Experts investigate whether rocket scientist Wernher von Braun might have found inspiration in technology found at the alleged UFO crash in Roswell. (S8, ep 3).

Alien Evolution: A look at the accounts of modern-day alien abductees. Plus, could the bizarre Paracas skulls discovered by Julio Tello be of extraterrestrial origin? (S8, ep 5).

The Other Earth: Ancient Alien theorists explore world mythology as they investigate whether extraterrestrials could be responsible for our existence. (S8, ep 6).

Hades: Discover the myth of ancient Greece's most feared god. Hades takes us behind the veil of the ancient Greek belief in life after death with chilling tales. (S1, ep 2).

Cougars and Fantasists: Meet the women who took Hitler under their wing, training him in the methods of high society and power - only to be left behind once he achieved it. (S1, ep 3).

The Princes in the Tower: Royal Blood: Richard III, whose body was recently exhumed, is linked to the deaths of two princes in the Tower of London in 1483. (S1, ep 5).

Inside the Tower of London: A look at an extraordinary display of nearly 900,000 ceramic poppies in the moat. Also, Curator Bridget explores a reminder of the horrors of war. (S1, ep 3).

Creatures Of The Deep: Experts investigate whether alien life forms are thriving in our seas, following Russian cosmonauts' discovery of living plankton in space. (S8, ep 7).

Circles from the Sky: Crop circles are a global phenomenon, with 10,000 seen worldwide. But are these strange patterns simply a hoax or could they be proof of UFO activity? (S8, ep 8).

The Alien Wars: Experts investigate whether the US military has a secret space programme, as well as evidence suggesting alien races have been in conflict for millennia. (S8, ep 9).

Our Place in the Universe: Discover the key role scientific pioneers played in reshaping our solar system. Plus, learn how technology helped humans explore its furthest reaches. (S1, ep 3).

The Code Breakers: Encryption is a key tool for keeping valuable information secret, but some ingenious minds have managed to crack impenetrable codes.

The Dunbar Armored Depot Heist: Allan Pace and five old pals plan and execute a daring robbery of Los Angeles based Dunbar Armored Car Company in 1997. (S1, ep 7).

Paranormal Destinations: Experts investigate the US government's experiments into teleportation. They also dig into strange happenings at Mount Shasta and Skinwalker ranch. (S1, ep 3).

Strange Triangles: Three places, three spooky stories. Experts examine weird sightings and unsolved disappearances at Bennington, Bermuda and Bridgewater triangles. (S1, ep 4).

Unidentified: What did UFO chaser Captain Mantell see before he was killed? Plus, experts investigate a close encounter in Texas and a mysterious crash at Shag Harbour. (S1, ep 5).

Creatures Of The Deep: Experts investigate whether alien life forms are thriving in our seas, following Russian cosmonauts' discovery of living plankton in space. (S8, ep 7).

Circles from the Sky: Crop circles are a global phenomenon, with 10,000 seen worldwide. But are these strange patterns simply a hoax or could they be proof of UFO activity? (S8, ep 8).

It's spring 1944 and on the Eastern Front, the momentum is firmly with allies as the war moves into its final, violent act. (S1, ep 7).

Chichen Itza: Considered one of the New Seven Wonders of the World, the Mayan City of Chichen Itza was the capital of a powerful civilisation. (S3, ep 4).

Taj Mahal: A walk through the iconic mausoleum complex, located in India and commissioned in 1632 by the Mughal emperor Shah Jahan to house the remains of his beloved wife.

The Alien Wars: Experts investigate whether the US military has a secret space programme, as well as evidence suggesting alien races have been in conflict for millennia. (S8, ep 9).

Love and Betrayal: Love is a universal and powerful emotion but it can also be destructive, lust can destroy and betrayal can wound. (S1, ep 4).

In 218 BC, a Carthaginian army set out to challenge the might of Rome. The route chosen by Hannibal has been disputed ever since and researchers believe they could now have the answer.