In the Da Vinci Code a lot is being said about Leonardo da Vinci's masterpiece The Last Supper. Dan Brown claims there are a lot of hidden messages hidden in the fresco, which is still on display in the Santa Maria Della Grazie church in Italy.
Robert Langdon tells Sophie Neveu in the De Da Vinci Code that the person who sits next to Jesus is not the disciple John. It is in fact Mary Magdalene. Langdon explains that this is clearly visible because the person next to Jesus looks female.
True? Untrue? It is hard to say anything about this. Leonardo da Vinci never said something bout it and we can't ask him why he painted John/Mary the way he did it.
According to most art historians the persons is most probably the disciple John. In the 15th and 16th century it was very common to paint John beardless and feminine. Even now, the disciple John is painted without a beard in most cases.
Tip:
Santa Maria Della Grazie, the church where you can admire The Last Supper, has a virtual tour on it's website. You can even zoom in on 'The Last Supper'.