A deserted amusement park and ruins of a top-secret military doomsday bunker hold secrets to a strange and forgotten past; experts investigate these remarkable feats of engineering to uncover how they were constructed and why they were abandoned.

A Mediterranean island paradise and a once-thriving South African community are now all mysteriously deserted and desolate landscapes; experts investigate the secrets of these remarkable places to uncover how they were built and why they were abandoned. This episode is a mashup of S07E03 "Secrets of Mafia Island," S05E03 "Haunting of Heartbreak Castle," and S05E04 "Kingdom of the Vanished."