Principal filming took place in the summer of 1948 at the Cinecittà studios in Rome. The amphitheatre scenes were filmed at the Arena di Verona. The production was then interrupted however for nearly a year, and was completed at the GTC studios at Joinville/Saint-Maurice in 1949. The film was released in France and Italy in 1950.
The film considerably simplified the plot of Lytton's novel, and there was some alteration of the names of the principal characters: Glaucus became Lysias, and Ione became Hélène; Nidia was made the victim of Arbax rather than an agent of his defeat. There were impressive set designs and costumes (Aldo Tommasini and Veniero Colasanti), and special effects by B. de Kerblay.
Marcel L'Herbier approached the project as one of the "chroniques filmées" ("filmed histories") which his film work had favoured during the past decade, giving some emphasis to the documentary aspects of the everyday life that had been preserved at Pompeii. He initially approached Albert Camus to write the dialogue (having in mind the latter's play Caligula), but in the event the task was undertaken by Alexandre Arnoux. L'Herbier admitted some reservation about the resulting film in spite of its strong cast and opulent settings.
Source : Wikipedia