Secret Nazi Bases

Why would the Nazi's pour so many resources into this strategically insignificant island, and hold onto it at all costs even at the end of the war when the end was surely near? What dark secrets lie buried in the tunnels, bunkers and watchtowers dotting Guernsey?

Nearly seven decades after D-Day, a massive Nazi artillery base the size of four football fields is found near Omaha and Utah beaches.

Built by a mysterious German engineer in an inhospitable location, the structure contains strange and suspicious tunnels, bunkers and more. Was this a secret Nazi base for Uboat resupply, or were there darker purposes for the house?

One of the largest bunkers ever constructed, the Blockhaus is built under immense secrecy, utilizing unimaginable engineering feats, and is a potential game changer for Hitler at the tipping point in the war.

A secret weapons program that could have ended badly for the allies. In the heart of Austria, a bunker and network of tunnels were discovered based on a long lost 1944 German report that indicated what the Nazis were up to.

As the Red Army approaches a forest in Poland at the end of the war, they stumble upon a massive complex containing over a thousand structures across 25 sq km. How did the Germans keep this colossal base secret from allied intelligence?