The production designer Alexander Trauner imported from France all the window glass used in the sets windows, as well as materials (iron for railings) used in the sets construction. The window glass was imperfect, wavy, with air bubbles. All the street shop windows, apartment mullioned windows were cut from this imported glass material. Parisienne street lamps, street fire hydrant plumbing hardware, as well as the sets' hardware for door latches, window latches, locks, were air-lifted to the States, delivered to the Goldwyn Studio for the feature. These items were matched, molded and fabricated in the film's staff shop, duplicated in fiberglass. The "L" plan of the three streets converging at the central street core conversion (at the) "Cafe Moustache" was designed in a theatrically forced perspective plan layout. The left side of the street extended through an adjoining (shared wall) stage door. The "T" plan of the central street extended to the rear stage wall, extremely forced in perspective. Minature French "toy" cars, approximately three feet long by fifteen, to eighteen inches high, were maneuvered on wires. The false perspective street raised in height above the stage floor approximately three feet. Scenically, the street's facade of shops were scaled and painted to recede as calculated for the reduced perspective horizon plane. Harold Michaelson, the film's illustrator, a genius at laying out perspective, calculated all the perspective plans and elevations for the three street ends. Atmosphere "extra casting" were hired, utilizing small (midgets) actors for all background action shots. Rain pipes were hung over the entire street set for the rain sequences, with the street's gutter system planned to flush the water out of the stage through stage wall drainage systems into the exterior adjacent studio street. The second story atelier set was located on the same stage, situated behind the street facade. This set was twenty feet off the ground, accessed by ladders. Fork lifts were used to deliver camera equipment and lighting equipment. The cast and crew had to use the ladders to climb up or down to and from the set. A minimum crew were allowed on the scaffold set with Jack Lemon, Shirley MacLaine and Billy Wilder. While filming their scenes in this small environment, the wonderful rapport between the two actors and Wilder was a "very private funny scenario". Behind this set, the scenic shop-department was located on the stage rear wall, with a paint frame and 20' high deck for the scenic artists to work from while painting the film's scenic drops. Additional stages were used for the "les Halls" and the Cathedral interiors. The beef carcass used for set dressing in the meat market were white plastic formed vacuums completely assembled. Twenty scenic artists painted these carcasses with oil paints, using sponges, fine hair paint brushes, using scenic techniques reproducing fresh marbled fat grained meat. All the cathedral stained glass leaded windows were also scenically oil painted on the imported French glass materials.
