Leni Riefenstahl has been hailed as one of the greatest directors of all time, even though her most famous films were works of propaganda for Hitler's Reich. Her film about the 1934 Nuremberg rallies broke new ground in cinematic techniques and had a huge influence on filmmakers for years to come. Riefenstahl always claimed she was just an artist, unaware of Nazi atrocities, but a new documentary reveals secrets from her extensive archives.