Salvator Mundi, a $450 million painting attributed to Leonardo da Vinci, has not been seen publicly since it sold at Christie's in 2017, the year it became the most expensive artwork ever auction.

Since its sale for a record US$450 million, the whereabouts of the Salvator Mundi, said to be painted by Leonardo da Vinci, has become one of the art world's greatest mysteries. On Monday ...