'Remarkable' discovery could shed new light on Mona Lisa Although part of the Royal Collection and recognised as a copy of the Mona Lisa, the background had been painted over in black for unknown reasons sometime in the late 18th century, therefore ruining the aesthetic and disguising its importance. As the later paint layers were stripped away, the appearance of a Tuscan landscape in remarkable condition and of such striking resemblance to the original led to further investigations being made. The replica provides clearer details of features obscured in the original, notably frilly edging on the neckline of Mona Lisa's garment, a sheer veil draped across her left shoulder, arm and elbow, and a sharper depiction of the spindles of the chair in which she is seated. The original, which is displayed behind bullet-proof glass at the Louvre in Paris, is obscured by cracked darkened varnish, making the woman appear much older than her true age. Because of its fragility, cleaning and restoration has long been considered to be too risky. But art historians believe the Prado's Mona Lisa reveals her as she would have looked at the time - a radiant young woman in her early 20s. "It gives a much more vivid impression of her enticing eyes and enigmatic smile," reported the Art Newspaper. The discovery of a contemporary copy of the Mona Lisa painted in the same studio of the master and developed alongside the original has been accepted by experts at both the Louvre and the Prado. Ana González Mozo, a technical specialist at the Prado, presented the findings at a conference on Leonardo da Vinci at London's National Gallery last month. She said that what was most exciting about the Prado replica is what it reveals about Da Vinci's original. In the Madrid copy, which is close in size to the original, there are areas that are better preserved than in the Louvre painting. What is more, a comparison of infrared reflectography on the two paintings, a process enabling conservators to peer beneath the surface, revealed similar sketching beneath the paint on both. Experts believe this suggests that the original and the copy were begun at the same time and painted next to each other, as the work evolved, even quite possibly while the model was present. The providence of the Madrid painting has now been re-evaluated. It is now thought to have been painted by one of Da Vinci's two favourite pupils - either Andrea Salai, who originally joined Leonardo's studio in 1490 and may have became his lover, or Francesco Melzi, who joined around 1506. Prior to its restoration, the Madrid replica did not even warrant its own entry in the inventory of the Prado's vast collection and had been hidden away in the bowels of the museum. It had been thought to be of Flemish origin and dating from at least a century later than the Mona Lisa. Museum authorities at the Prado said on Wednesday that it was an "incredibly important discovery" and the earliest known copy of the Mona Lisa. "It is as if we were in the same studio, standing at the next easel," said Gabriele Finaldi, the Prados deputy head of collections. But the museum team declined to comment on the monetary value of the piece saying only that it was "invaluable" The fully restored replica is expected to be unveiled at the Prado in Madrid in mid-February and will then be lent to the Louvre where once again, 500 years after they were separated, the two versions will hang side by side again.