Crowds are gathering at Madrid's Prado Museum to view a copy of the Mona Lisa for the first time since a restoration revealed it was almost certainly painted by one of Leonardo da Vinci's apprentices as he worked on the original.

The painting was put on display at the museum on today, where it will stay until it moves to Paris' Louvre museum next month to hang alongside the original as part of an exhibition on da Vinci's work.

Although the precise author of the copy has not been determined, both the Prado and Louvre believe it is probably the earliest known copy of La Gioconda.

The copy has been part of Spain's art collection for hundreds of years. It had previously been on display in the Prado but no one paid much attention as it was considered a mediocre copy.