Abandoned Engineering S04E05 - Tunnel to the Underworld

A ghostly town in West Virginia that fell victim to the pace of change when steam trains were rendered obsolete. A colossal dry dock structure on the American west coast may now be crumbling but has written itself into military folklore. An elaborate underground complex in Italy that had been abandoned for nearly 2000 years, continues to mystify explorers today. And an island paradise in Costa Rica hiding a grim history of violence within an old, abandoned prison. But how and why were they ever built at all, and why are they now left abandoned?