I have detected, that Leonardo da Vincis painting Mona Lisa contains a second, male face, which is part of the female. You can see the other face, by looking at the female face with nearly closed eyes, so that you barely see something. (Please click on the left image below first, so that you see the original painting alone. The oftener and longer you look on it this way, the better you see it.)
The other face is slender, has other eyes, another hairstyle, another facial expression and is male. Through the flicker of the nearly shutted eyes, there is dynamik. It seems to follow one with the eyes, and change the facial expression, as if it would be alive. There is a broad spectrum of facial expressions.
In the right image I have tried to mark the other face by changing the contrast and brightness of the image (apart from that is nothing changed). On this way is going lost aplenty, but one can recognize the different eyes well.
I found in the internet the informations, that the Mona Lisa shall express a male or shall exhibit male marks, but not, that it is a
ambiguous image
or
multistable perception. Therefore I consider that as my original discovery for now.