Mysteries of the Abandoned - 4 ª Season

The world's strangest ghost towns are home to dark secrets, creepy buildings and eerie sights; new discoveries reveal why they were abandoned.

Yugoslav strongman Josip Broz Tito's secret Cold War military compound on the Croatian island of Vis, San Francisco's Sutro Baths, Australian Convict Sites in Port Arthur, Tasmania, and Hitler 's unfinished Deutsches Stadion in Nuremberg.

The ruins of a once-palatial compound contain the secrets of one of history's most notorious criminals, and new discoveries reveal why this high-security estate was built and why it was abandoned.

Tunnels filled with human bones lie beneath the streets of Paris, and this horrifying engineering marvel points to a dark secret. New discoveries reveal why this grisly underground death maze was built, and why it was abandoned.

A ghost town in the American West was once a Gold Rush hotspot and one of the most violent places in America. Today, there are legends of a secret treasure buried in the surrounding hills, and new discoveries might finally reveal its true location. Also, in remote southern Poland, the Nazis used slave labor to create a vast underground maze of tunnels, the purpose of which still is not fully understood. And, at the southwestern tip of England in Cornwall, bizarre circular mounds are found near ruins. Copper and tin were mined here, but the production of a deadly chemical surged in the 19th century when the mines began to play out. Also, a site in Germany (Wünsdorf) that changed drastically in March 1994 is examined.