the flesh Maria is associated with religion, and by extension righteousness.  When she's addressing all the workers in the catacombs she's standing in front of a bunch of crosses.  But you can also see the distorted shadows of the crosses in the background.  I'm not sure how that fits in, but it probably means something.  Maria spends a lot of time and energy announcing that Freder is the "heart" and that he's going to save the world.  I think that Maria did just as much active saving as Freder.  The book of revelations talks about false prophets being a sign that the real messiah is coming soon.   and there was a false messiah in Metropolis, the robot Maria. Maybe the distorted shadow crosses behind Maria in the catacombs had something to do with the flesh Maria and the robot Maria being part of the same whole.  If the flesh Maria had not been so perfect, perhaps the creation of the robot alter ego would not have been necessary to complete her self? I'm not sure I really think that.  It's just a thought.