For generations the enigmatic smile of the Mona Lisa has captured the imaginations of thousands of visitors to the Louvre. But now the mythology surrounding the world’s most famous painting is being questioned by the unveiling of a supposed second version of the portrait. The painting, purporting to show a younger portrayal of Leonardo da Vinci’s muse, will be presented in Geneva today by the Swiss-based Mona Lisa Foundation. But some art experts are highly sceptical and contend the work is more likely to be a later copy. The “younger version” – which may have been painted around 1505 – is not new to the art world but has been locked away in a Swiss vault for many years.