Not professional actors, but prisoners of the Civitavecchia gaol took part in the movie shooting. It is noteworthy that the directors focus not so much on the mimicking part of the acting, but on the dialogues. Their richness makes us perceive the film as play, except it has audio-visual and expressive means. The frames and mise en scene are arranged like geometric shapes and use all the existing methods of constructing the composition. Fortezza — even though it has its atmosphere — is like an inside-out mockumentary. This is also present in the cameraman's tricks — a shaking hand-held camera and unexpected defocusing, in non-professional actors, in a narrative that captures the everyday life and reality of the fortress rather than a twisted plot.
This is not the first time the novel is adapted for the screen — in 1976 another film was directed by Valerio Dzurlini. In contrast to this version, Fortezza is distinguished by minimalism — the absence of stars in the cast, short duration, general summary of the novel — without the character's names and the main plot twists, as well as the lack of action as such: the characters talk without moving much.