An alien Nazi structure that changed history, a strange Soviet monolith known as the Tower of Death, and a concrete ocean giant are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.

A strange deserted city in America's heartland, an eerie gigantic wall deep in snowcapped mountains, and a mysterious top-secret Soviet facility are deserted engineering projects, and new discoveries reveal how they were built and why they were abandoned.