 In 2005 , an expert at the University Library of Heidelberg discovered a margin note in the library 's collection that established with certainty the traditional view that the sitter was Lisa . The note , written by Agostino Vespucci in 1503 , states that Leonardo was working on a portrait of Lisa del Giocondo . The Mona Lisa has been in custody of France since the 16th century , when it was acquired by King Francis I ; after the French Revolution , however , it came into the possession of the people . Today about six million people visit the painting each year at the Louvre in Paris , where it is part of a French national collection . 
