Bar at the Folie Bergère by Édouard Manet

Leftt: "Bar at the Folie Bergère", 1881, by Édouard Manet.
Right: Detail

This is a very famous of Manet's painting.
At the back of the girl there is a mirror showing the scene in front of her and she doesn't seem to pay attention to any particular person or event.
Take a look at her image at the mirror at the right side of the painting. The mirror shows what is parallel to the girl but her back is painted in another angle as if it was another mirror. The man looking at her should also be depicted as if he was facing us.
Manet's solution is far more interesting and accurate than if he had painted it following the mirror's rules. This is far more warm and, why not, realistic? I believe that if we were in front of the girl our heads would turn to see the man.