The search for Nazi secrets and their stolen gold continues in the darkest corners of history; both underground and underwater. This time, Josh dives for relics of Nazi foreign minister Joachim Von Ribbontrop who dumped his family's entire fortune into the dark and deep waters of Lake Fuschlsee in the Austrian Alps. In order to learn if the Nazis where building an atomic bomb, he starts his quest for answers in Hitler's hometown of Linz. Then, he stops at the Mauthausen-Gusen concentration camp memorial in Sankt Georgen an der Gusen to pay his respects to the hundreds of thousands who perished here. He also explores 25 miles of tunnel under the Bergkristall complex, the largest secret underground facility ever built. It was designed by SS General Hans Kammler to oversee the Nazis nuclear project.