Harbou and Lang collaborated on the screenplay derived from the novel, and several plot points and thematic elements—including most of the references to magic and occultism present in the novel—were dropped. The screenplay itself went through many rewrites, and at one point featured an ending where Freder flew to the stars; this plot element later became the basis for Lang's "Woman in the Moon". The time setting of "Metropolis" is open to interpretation. The 2010 re-release and reconstruction, which incorporated the original title cards written by Thea von Harbou, do not specify a year. Before the reconstruction, Lotte Eisner and Paul M. Jensen placed the events happening around the year 2000. Giorgio Moroder's re-scored version included a title card placing the film in 2026, while Paramount's original US release said the film takes place in 3000. A note in Harbou's novel says that the story does not take place at any particular place or time, in the past or the future. "Metropolis" began principal photography on 22 May 1925 with an initial budget of 1.5 million Reichsmarks. Lang cast two unknowns with little film experience in the lead roles. Gustav Fröhlich (Freder) had worked in vaudeville and was originally employed as an extra on "Metropolis" before Thea von Harbou recommended him to Lang. Brigitte Helm (Maria) had been given a screen test by Lang after he met her on the set of "Die Nibelungen", but would make her feature film debut with "Metropolis". In the role of Joh Fredersen, Lang cast Alfred Abel, a noted stage and screen actor whom he had worked with on "Dr. Mabuse the Gambler". Lang also cast his frequent collaborator Rudolph Klein-Rogge in the role of Rotwang. This was Klein-Rogge's fourth film with Lang, after "Destiny", "Dr. Mabuse the Gambler", and "Die Nibelungen". Shooting of the film was a draining experience for the actors involved due to the demands that Lang placed on them. For the scene where the worker's city was flooded, Helm and 500 children from the poorest districts of Berlin had to work for 14 days in a pool of water that Lang intentionally kept at a low temperature. Lang would frequently demand numerous re-takes, and took two days to shoot a simple scene where Freder collapses at Maria's feet; by the time Lang was satisfied with the footage he had shot, actor Gustav Fröhlich found he could barely stand.