The Reich Underground (2004)

Original title: Das unterirdische Reich. Die geheimen Welten der Nazis

In 2004, director Michael Kloft (The Goebbels Experiment) accompanied government historians and surveyors as they inspected various underground tunnels, bunkers, and silos built by the Nazis between 1940 and 1945. Some, mainly in Germany and occupied Poland, were built as shelters to house high-ranking Nazi officials like Adolf Hitler, Joseph Goebbels, and Martin Bormann. Others, in the northern coast of occupied France, were constructed by Armaments Minister Albert Speer to serve as massive missile silos to launch V2 rocket attacks against London and, eventually, the United States. Interviews with surviving slave laborers and SS officials tell the story of how and why these tunnels were built. (from dvdverdict.com)