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.