Olympia, Leni Riefenstahl’s four-hour 1938 documentary—a purported masterpiece on the Berlin Olympic Games—is impossible to get through in its entirety. You can’t do it, not without several thumb leans on “Fast-Forward” to skip the dull parts. Her work has that in common with porn. It shares lots of the same characteristics, actually: an obsession with slick, perfect athletic bodies; monotony; repetitive floggings; manipulated states of arousal.

The way to view Olympia is to sample it after watching the new documentary Riefenstahl, directed by Andres Veiel, a film that is genuinely impossible to turn off or away from. That work, which is now available for American audiences to stream, will be of interest to anyone concerned about the seductive creep of Nazism on a populace, especially given the tenor of modern right-wing movements in Europe and America. After World War II, Riefenstahl insisted that she was a “naive,” apolitical artist who had simply pursued her aesthetic obsession with “beauty” and knew nothing of the Nazi atrocities as they were happening. Veiel, an award-winning German filmmaker whose previous subjects include the left-wing terrorist group Baader-Meinhof and a Jewish-Palestinian collaborative-theater company, set out to resolve the questions of whether she was truly Nazi-neutral, and whether her aesthetic was really so innocent.

These questions are important, given Riefenstahl’s enduring influence; her work is still taught in cinema classes for her monumental camera shots.