Since detailed records of the Wannsee Conference did not survive World War II, minor details of the movie (such as the seating arrangement at the conference table, what was actually served for lunch, and who was wearing a uniform compared to who wasn't) were totally up to the guess of the producers, and not based on any historical evidence. The producers and writer did have access to more primary material than it might seem at first. During his trial in Israel, Adolf Eichmann provided many details about the subject of the movie, even down to specific conversations, the general tone of the meeting, and other details. In particular, it's worth noting that a good bit of the dialogue in the movie is lifted verbatim from relevant memos and speeches by Nazi officials that were preserved, are part of the historical record, and cited by numerous sources. Many specific locutions used by the men in the movie can be found as cited, for instance, in Gitta Sereny's book "Albert Speer: His Battle with Truth" as well as other sources. The single-page, neutered summary of the meeting that survived in the files of the German Foreign Office is far from the only primary source used by the filmmakers.
The house shown when General Reinhard Heydrich (Sir Kenneth Branagh) is shown flying into the conference is the house of the original conference. The inside of the house shown in the movie, however, was made for this movie.
This production used an almost theatrical performance style during shooting. The performers stayed in costume and character from the start to the end of each day of filming. A set was used with solid (non-moving) walls and ceilings, to reinforce the reality of the setting, and eliminate any delays for changing camera or lighting set-ups. The action was filmed in extremely long sequences, sometimes twenty pages or more of script at a stretch, which is unusual in this type of production. However, many of the actors had a Shakespearean background, and having to memorize this amount of dialogue was not a new experience for them. The production style required the use of the Super 16 film format. This was needed, because of the longer film magazines available for those cameras, and also the smaller size, allowing the cameras to get in very close to the performers sitting around a conference table, the setting used for the bulk of the story.
The opening and closing of this movie have Reinhard Heydrich (Sir Kenneth Branagh) flying to and from the Wannsee Conference, which took place on January 20, 1942. However, Heydrich was officially grounded by Heinrich Himmler after he was shot down by Russian anti-aircraft in late 1941.
The address of the stately home used for the exterior shots is Am Großen Wannsee 56-58, 14109 Berlin Germany. It is the actual villa that the Nazis used for the Wannsee Conference held in January of 1942. It was established as a historical museum and memorial to the victims of the Holocaust in 1992. The interior shown in the film is a set. The architecture and interior decor of the meeting room is faithfully recreated as it appeared at the time of the conference.