Mona Lisa copy goes on show in Prado

The restored painting (right) offers more detail than the original (left)

A copy of Leonardo Da Vinci's Mona Lisa, believed to have been painted at the same time as the original, has gone on display at Madrid's Prado museum.

The work, which has just been fully restored, is thought to have been painted by a Da Vinci assistant.

"I think what's important is it enables us to understand how Leonardo worked in his studio," said deputy director of conservation, Gabriele Finaldi.

The painting moves to the Louvre in Paris for an exhibition in March.

The original hangs in the Parisian gallery so this will allow visitors to compare the two works.

A black layer of paint on the Prado copy was removed as part of the restoration process - this revealed details in the landscape which experts say is evidence the replica was made at the same time Da Vinci painted the original.

The restoration process took two years.

Too risky

Experts discovered that the Prado version was painted on a walnut panel. This wood was used for other small-format panels by Leonardo and his studio, including The Lady with the Ermine and Saint John the Baptist.

The high quality of the materials used in the creation of the Madrid version suggests that it was an important commission.

The Prado's Mona Lisa has been in the museum since it was opened in 1819.

The newly-revealed painting will be on display there until 13 March.

There are dozens of surviving Mona Lisa replicas from the 16th and 17th Centuries - when copying famous artworks was a thriving business.

The original painting, dating from the early 16th Century, is obscured by several layers of old, cracked varnish.

However, cleaning and restoration is thought to be too risky because the painting is fragile.