A massive, alien-like fortress built into a mountainside is the central node to a network of pipelines that race outwards like tentacles; behind-the-scenes access reveals the secrets of why this strange complex was built and why it was abandoned.

The ruins of an abandoned prison are evidence of a chaotic riot that put the prisoners in charge; special access to its burnt-out interior reveals how inmates took over Ireland's Alcatraz and why it is deserted today.