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.
Isleworth Mona Lisa
In October 2013 Jean Pierre Isbouts published a book titled "The Mona Lisa Myth" examining the history and events behind the Louvre and Isleworth paintings and confirmed the latter's attribution to Leonardo. A companion film was released in March 2014. In April 2014, Albert Sauteur examined the perspective used to execute the "Isleworth Mona Lisa" and the "Mona Lisa" in the Louvre, and concluded that Leonardo painted both works. In July 2014 "The Mona Lisa Mystery" premiered on the PBS television station's series "Secrets of the Dead". This documentary investigated, at length, the authenticity of the Isleworth painting.