When Casanova is running away from the Inquisition in the opening scene he jumps through a window and into the University of Venice. The University of Venice never existed and the building he jumps into is in fact the "Theatro Olympico", one of the first Renaissance theatres- and 140 kilometers away from Venice.
During the short sword fight at the end of the film when they are running away Oliver Platt takes off his cape and fights with it just as Oliver Reed did as Athos in The Three Musketeers (1973). Oliver Platt played Porthos in the 1993 version of The Three Musketeers (1993).
Francesca Bruni was not a real person. The character name is taken from the Bob Hope film 'Casanova's Big Night'.