Mona Lisa

Observers of the Mona Lisa before the 19th century saw nothing mysterious in her smile.

An excerpt from the article 38 facts about Mona Lisa
At the time, the smile was said to be "more divine than human," but this was attributed to the unusual position of the Leonardo da Vinci model. Later interpreters of the smile saw in Mona Lisa as a femme fatale figure or "one of the courtesans of the 16th century." Others saw the experience of all historical epochs and "a symbol of the modern idea" in this smile.