One of the most famous paintings that were produced by Da Vinci was the 'The Last Supper'. From 1495 to 1498 he worked on it, it is 15 feet tall and 29 feet wide. The painting was made using experimental pigments directly on the dry plaster wall unlike frescos, where the pigments are mixed with the wet plaster; it has not stood the test of time well. Even before it was finished there were problems with the paint flaking from the wall and Leonardo had to repair it. Over the years it has crumbled, been vandalized bombed and restored. Today we are probably looking at very little of the original. The 'Mona Lisa' is the most well-known painting, and arguably the most famous painting in the world. However, the sitter can be identified with some confidence as Lisa Gherardini, the wife of a prominent Florentine silk merchant Francesco del Giocondo who may have commissioned it to mark his setting up home and the birth of his son, Andrea. The picture was begun in Florence around 1503-04 but was probably not finished until much later, possibly as late as 1516. The painting was never delivered to its commissioner; da Vinci kept it with him until the end of his life. Today, the "Mona Lisa" hangs in the Louvre Museum in Paris, France, secured behind bulletproof glass, and is regarded as a priceless national treasure.