First, the actors use the actual languages of their roles. The Russian soldiers speak only Russian; the Hungarians only Hungarian; the Germans only German, except to the minimal extent to tell the story. Since Debra Kerr is English, she speaks only English, and, of course, Yul Brynner and a few others essential to the story also speak heavily accented English. As a result, the empathy of the audience to the travelers becomes paramount. The viewer shares all the confusion and suspense of being involved in an illicit border crossing when he/she cannot understand any of the languages spoken around them. Very powerful feelings are aroused in the audience, and notwithstanding the heavy use of foreign languages, the audience is never at a loss for following the film. No subtitles are necessary.
Second. I was in Hungary in 1995, and I'm telling you, this movie has it right on. From the gypsy music overpowering the dinner meal to the underground caverns in the buildings where much of the action takes place to the village scenes, the realism is incredible. If I didn't eat in the actual restaurant in the movie, I ate at its double. I thought that I actually walked down the main street in that village. (Actually, the film was shot in Austria).
Third, and most important, this movie reunites Deberah Kerr and Yul Brynner (after The King and I) and the magnetism between them as the story unfolds is nothing short of Oscar qualified. Of course, Yul already received an Oscar for playing that relationship, so the Acadamy wasn't going to give him another one, but that is the quality of the film. Don't miss this one.