After recently reading a book called "The Vatican Exposed" i have learnt that a lot of things portrayed in The Godfather 3 are actually true facts.
Firstly it is almost certain that the church had John Paul 1st murdered due to his views on reform
Secondly it is true that A Vatican Banker was murdered and hang underneath a bridge much like Reizig at The end of part 3
It is also true that the company known as Imobiliare was indeed controlled by a Mafia Banker called Michele Sindonna, this just goes to show that not only is The Godfather 3 a great stand alone film, it is actually an accurate representation of The Corruption in The Catholic Chruch at that point in history