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.

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.

Concrete channels hidden in a mountaintop forest, a collapsing bridge, a marooned military base and the upright rusting carcass of ship.

A towering structure with an explosive past, a deserted cityscape, a mysterious top-secret facility and a vast Nazi construction.

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.

Hidden tunnels that saw a city prosper, a sunken wreck with a remarkable past, a concrete wartime dome and a mysterious Cold War building.

A village ruin, pitted and scarred, a ghostly fleet of ships, a bridge to nowhere hidden in a forest and strange metal structures in a wood.