The Mona Lisa is arguably the most famous painting in the world due to a variety of factors that include its painter, Leonardo da Vinci, the fact that he left very few completed paintings, the mysterious circumstances surrounding the painting, and the fact that it was stolen and lost for a number of years. It is housed in the Louvre, which is the most visited art museum in the world. When you combine all of these things, it makes the Mona Lisa probably the most visited/overcrowded painting in the world. Seeing it without the heaviest crowds is a matter of experience, opportunity, and very good timing.