What on Earth? säsong 4

Satellite images reveal a series of large mounds in Romania, just a few miles from the home of Vlad the Impaler. Could these mounds be Dracula's long-lost grave?

A strange structure might point the way to a lost civilisation's fountain of youth. Also, bizarre marks across the eastern US leave experts baffled.

A ghost ship with links to the mob suddenly appears on a California beach. Plus, a lake believed to have magical healing powers holds clues to life on Mars.

A ghost town covered in a strange, white powder emerges from a lake in Argentina. Plus, a declassified CIA image uncovers a bizarre, giant Soviet weapon.

A forest of razor-sharp stones could be home to an undiscovered humanoid species. Satellite imagery reveals a mysterious eye-shaped island in a swamp.

New data from NASA satellites might reveal a lost continent in the Indian Ocean, images of a South American island reveal strangely Germanic buildings and a pit of bodies suggests fears of a zombie nightmare.

A strange lake in Transylvania is the home of an abandoned village and a terrifying secret. When a labyrinth is discovered on an island once home to an ancient Greek civilization, experts investigate if it was the legendary home of the Minotaur.

Could a 1945 reconnaissance photo reveal the hometown of Biblical giant Goliath? Also, strange, otherworldly formations lie on the seabed near the Bahamas.

An abandoned city in remote jungles could be the home of an ancient treasure. Also, could a mysterious stone circle be the fabled round table of King Arthur?

When experts investigate a network of tunnels rumoured to be the hiding place of lost royal treasure, they find evidence of human sacrifice for a Viking god.

Can satellite images help identify the hiding place of the Nazi Gold Train? Also, a blood-red river in Siberia points to pollution on a catastrophic scale and a discovery of a long-lost settlement rewrites the history of the Vikings in North America.

When NASA discovers a strange pattern in the Arctic ice, experts investigate if it has alien origins. Also, a mystery in the Sahara could have a sinister explanation that need more investigation.

Man-made islands are spotted near a North Korean missile facility. Also, a discovery in Siberia could reveal a mission to the centre of the earth. An unexpected find in a remote desert leads experts to a lost city of giants.

An abandoned city in the African jungle may have a bloody past of malevolent spirits and cannibals. Experts investigate and delve into Hitler's secret Nazi UFO program.

Experts investigate a strange glowing lake reported to turn things into stone. Also, a dark conspiracy could be at work in the Australian outback.

A mysterious Stonehenge-like structure in Russia might have links to the Nazis. Experts uncover clues to a mega-tsunami with the power to ravage the United States.

New discoveries lead to a crypt rumoured to hold the Ark of the Covenant. When a great white shark is killed in the ocean, experts suspect an ocean monster is lurking beneath the waters.

Treasure hunters have searched for a lost Incan city of untold wealth for a century. With the use of new technology, the riches of the lost Incan city could finally be located.

A ghost ship is found on a remote island, home to one of Earth's last uncontacted tribes. New evidence reveals a mysterious military compound in Russia.

New evidence suggests how the Mayans vanished. Scientists find traces of ritualistic drug binges from the ancient world, when they investigate a deserted settlement.