Verona - we have a problem...

If I say "Romeo and Juliet" to you, what's the first thing that comes into your mind? I imagine for many if not most of you it will be the balcony scene - you know "...but soft, what light through yonder window breaks,,,".  And that quote in fact contains the word which is the nub of the problem. My Complete Works of Shakespeare - a Christmas present from my Gran when I was 15 - has the stage direction "Juliet appears above at a window".  So in Shakespeare's original text, there was no balcony - Juliet was inside, behind a window.  Indeed the word "balcony" and the concept of an upstairs outdoor terrace was unknown in Shakespeare's time.  So how come any production of the play almost inevitably has Juliet standing at the balustrade of a balcony? How come you can go to Verona and see the Casa di Giulietta complete with balcony? It's a bit complicated, so I'll leave that until tomorrow.