At 1:33:20, when the two elderly ladies are visiting Barny, the background behind the window is clearly fake, revealing it was a studio set.
At several points in the movie, you can see extras looking towards the camera or the crew. For instance, the bystander on the right side of the screen at 4:40 in the street when the Italian soldiers are surrounded by giggling women, or in the church at 1:43:40, when the choir kid is looking behind him, while the countershot shows there is nothing to look at.