The United States is home to countless eerie and abandoned places; and using the latest tech, experts make new discoveries to reveal the secrets of how they were built and why they were abandoned. The segments of this special come from various episodes.

The Nazis built secret megastructures during their bloodthirsty quest for world domination, but today, they're now abandoned; experts are rediscovering these lost places to reveal the mysteries of how they were built and why they were deserted. The segments of this special come from various episodes.