Mona Lisa replicas and reinterpretations
After restoration, the Prado's "Mona Lisa" revealed details covered by previous restorations and layers of varnish.
Furnishings and fabrics were enhanced, as well as landscape and facial features.
It is anticipated that such revelations may offer further insight into Leonardo's original.
Experts at the Louvre reportedly supported the Prado museum's findings.
The Prado replica was subsequently transported to the Louvre in 2012 to be displayed next to "Mona Lisa" as part of a temporary exhibition.
Two nude paintings bearing similarities to Leonardo da Vinci's original were part of a 2009 exhibition of artwork inspired by "Mona Lisa".
Displayed at the Museo Ideale in Leonardo's hometown of Vinci, near Florence, some believe one of the paintings – dating from Leonardo's time – to be the work of Leonardo himself, and it has at times been credited to him.
Other experts theorize the painting, one of at least six known to exist, may be just another copy painted by "followers" of Leonardo.
Scholarly dispute persists as to artist, subject and origin.
The nude in question, discovered behind a wall in a private library, reportedly belonged to an uncle of Napoleon Bonaparte, who owned another of Leonardo's paintings.
Facial features bear only vague resemblance, but landscape, compositional and technical details correspond to those of the "Mona Lisa" known worldwide today.
Mona Lisa replicas and reinterpretations
"Mona Lisa"'s iconic face has been available for years in all forms, reproduced on everything from birthday cards to refrigerator magnets, appearing in advertisements for fashion and travel industries, and on the cover of magazines.
Leonardo da Vinci's own status as "genius" has been suggested as a factor contributing to the mystique of his creation.
The eyes of Leonardo's original "Mona Lisa" appear within cover-graphics for Dan Brown's fictional novel "The Da Vinci Code".
The "Mona Lisa" portrait also appeared in the teaser trailer for the 2006 film of the same name, although a replica was used for filming, appears only briefly in the film, and plays a very small part in the story.
Along with Vermeer's "Girl with a Pearl Earring", "Mona Lisa" is among the most replicated works of art.
The sheer number and variety of replicas and reproductions since its creation in the early 16th century illustrates a so-called "self-reinforcing dynamic"; utilized in advertising because of its familiarity, thereby re-enforcing its fame.