Leonardo painted the Last Supper in the Refectory of the convent of Santa Maria delle Grazie at the behest of Ludovico il Moro, in a period of time ranging from 1494 to 1497. The artist, being a wall painting, did not rely on traditional as well as resistant fresco technique, which requires a quick application of the color on the still damp plaster, but wanted to experiment with an innovative method that would allow him to intervene on the dry plaster and, therefore, to be able to return to the work several times taking care of every detail. Unfortunately, Leonardo's intuitions turned out to be wrong and soon, due to an unfortunate concomitance of causes, painting began to deteriorate. Over the centuries, consequently, many restorations followed one another in a desperate attempt to save the masterpiece. In 1999, after more than twenty years of work, the last conservative intervention was completed which, thanks to the removal of many repaintings, brought to light what remained of the original drafts. In Lombardy, among the sites recognized by UNESCO as "World Heritage" we find Milan with the complex of the Dominican Church and Convent of Santa Maria delle Grazie and one of the most famous paintings in the world: Leonardo da Vinci's Last Supper, two masterpieces absolute worldwide. The complex was included in the Unesco Heritage list in 1980, testifying to a culture rich in values to be transmitted to humanity, which gravitates around the regional capital.