query: Where is the Mona Lisa painting located today?
passage: Mona Lisa
The painting is thought to be a portrait of Lisa Gherardini, the wife of Francesco del Giocondo, and is in oil on a white Lombardy poplar panel. It had been believed to have been painted between 1503 and 1506; however, Leonardo may have continued working on it as late as 1517. Recent academic work suggests that it would not have been started before 1513.[4][5][6][7] It was acquired by King Francis I of France and is now the property of the French Republic, on permanent display at the Louvre Museum in Paris since 1797.[8]
passage: Mona Lisa
Because the Mona Lisa's poplar support expands and contracts with changes in humidity, the picture has experienced some warping. In response to warping and swelling experienced during its storage during World War II, and to prepare the picture for an exhibit to honour the anniversary of Leonardo's 500th birthday, the Mona Lisa was fitted in 1951 with a flexible oak frame with beech crosspieces. This flexible frame, which is used in addition to the decorative frame described below, exerts pressure on the panel to keep it from warping further. In 1970, the beech crosspieces were switched to maple after it was found that the beechwood had been infested with insects. In 2004–05, a conservation and study team replaced the maple crosspieces with sycamore ones, and an additional metal crosspiece was added for scientific measurement of the panel's warp.