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There's often more to a picture than meets the eye, and many of the world's most famous artworks have secrets hidden beneath the surface.
Several famous paintings are known to cover older works by the artist that can now be detected by scientific techniques like X-ray fluoroscopy, revealing the original paintings and drawings that would otherwise be lost to history. In other cases, works of art feature cryptic clues placed by the artist, or contain curious resemblances — and some have even sparked popular conspiracy theories.
Here are 11 hidden secrets in famous works of art.
The Arnolfini Portrait by Jan van EyckSlide 2 of 23
The Arnolfini Portrait by Jan van EyckThe Arnolfini Portrait by the Dutch painter Jan van Eyck is thought to portray an Italian merchant named Giovanni di Nicolao Arnolfini and his wife, who lived in the Flemish city Bruges.
The painting is celebrated for its vivid and detailed representations of the couple and their surroundings, and the precise geometry of its composition, which includes an intricate reflection of the scene in a framed circular mirror hanging on the wall of the room.
The details of the painting have fueled many theories about its hidden symbolism, from the way the couple is joining hands, to the meaning of the small dog, the carelessly placed pairs of shoes, and the single lit candle in the chandelier. The artist's signature also appears as graffiti on the wall of the room: "Jan van Eyck was here, 1434."
The circular convex mirror on the wall near the center of the painting reveals an intricate reflection of the room as the scene was painted — including two additional figures standing beside the doorway, one whom may be the artist himself. It's not known if van Eyck used a real convex mirror to paint the scene from behind, but the curved distortions of the image are almost optically perfect, experts have said.
A contentious theory from the 1930s holds that the scene is a representation of the marriage of the couple, and that the mirror image and van Eyck's dated signature are designed to serve as a legal record of the marriage, including the two witnesses required to be present. But, this theory now finds little favor with most art historians and with the curators of the National Portrait Gallery in London, England, where the painting is now on exhibit.
The distinctive Arnolfini Portrait is often referenced and parodied in popular culture, including a Muppet version featuring Kermit the Frog and Miss Piggy. In Ridley Scott's 1982 science-fiction movie "Blade Runner," bounty hunter Rick Deckard (played by actor Harrison Ford) find clues about the androids he is chasing by zooming in on the reflection in a circular, convex mirror that hangs on the wall of a room in a photograph.Slide 3 of 23
The Blue Room by Pablo PicassoSlide 4 of 23
The Blue Room by Pablo Picasso
The Blue Room is regarded as one of Pablo Picasso's earliest masterpieces. It was painted when Picasso was 19 years old and living in Paris, and is one of the first works of his early "Blue Period" of melancholy scenes dominated by varying shades of blue.
In 2014, scientists announced that they had found a hidden image underneath the painted surface of "The Blue Room," showing the hidden portrait of a man wearing a bow tie, resting his chin on his hand, reported the Associated Press.
It's not yet known who the mystery man could be, but it's definitely not a portrait of Picasso himself. One possibility is the art dealer Ambroise Vollard, who hosted Picasso's first show in Paris in 1901.
Art historians say Picasso was poor but very productive at the time he painted "The Blue Room," so it wasn't unusual for him to reuse an earlier canvas for a new idea.Slide 5 of 23
Mona Lisa by Leonardo da VinciSlide 6 of 23
Mona Lisa by Leonardo da Vinci
French scientist Pascal Cotte announced earlier this year that he'd found a hidden image of a different woman beneath the world's most famous portrait, Leonardo da Vinci's Mona Lisa.
Cotte was able to examine the Mona Lisa at the Louvre Museum in Paris in 2004 under intense lights of different frequencies. He then spent more than 10 years analyzing the data from these experiments. Cotte said his research has revealed the original portrait on the Mona Lisa canvas, but it portrays a different woman who is looking off to the side instead of directly at the artist.
Da Vinci painted the Mona Lisa in around 1506. It's generally thought to portray Lisa Gherardini of Florence, the wife of a silk merchant.
But, Cotte thinks the original Mona Lisa shows a different Florentine woman of the time named Pacifica Brandano.
Not all art experts are convinced by Cotte's research, however. One art historian suggested his methods may have created an artificial image from the original brush stokes used by Leonardo to create the final portrait, but they did not represent a different portrait.Slide 7 of 23
The Last Supper by Leonardo da VinciSlide 8 of 23