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.
Bobbio
Bobbio is located in the heart of Val Trebbia, a valley described by Ernest Hemingway as "the most beautiful in the world". The town is nestled at the foot of Monte Penice, above sea level, on the left bank of the river Trebbia.
Its history is identified with the Abbey founded in 614 by St. Columbanus an Irish missionary, and as a result it became one of the principal centers of religious culture in medieval Italy, home to a famous library and basilica. The possessions of the abbey in the Lombard and Carolingian eras spanned the north of Italy.
Bobbio is a coveted tourist destination known for its history of art and culture, for nature lovers, and for its ancient monuments. It has from antiquity been a crossroads between different cultures such as the Piacentine, Ligurian, Piedmontese, and Pavian.
The historical center and heart of the city has maintained the characteristics of the medieval village.
One town landmark, the Ponte Vecchio, called "Ponte Gobbo" (Hunchback Bridge), also known as the "Devil's Bridge", is an ancient stone bridge of Roman origin, which crosses the river Trebbia in eleven irregular arches. 
The Shrine of Our Lady of Penice, located on top of Monte Penice, dominates the landscape, and is also popular in winter for its ski resorts.
Historians have speculated that Bobbio was the town in which Leonardo da Vinci completed the Mona Lisa.
Carla Glori in December 2011 has published her book "Enigma Leonardo:decifrazioni e scoperte" where the background of the portrait has been identified as the landscape of Bobbio.