The Last Supper by Leonardo da Vinci is located in the refectory of the Convent of Santa Maria delle Grazie and it was commissioned by Ludovico il Moro. The painting is based on the Gospel of John and it depicts the moment when Jesus announced that one of his disciples would betray him. The Last Supper measures 460 cm × 880 cm (180 in × 350 in).
Because a fresco cannot be modified as the artist works thus the details can’t be perfect since the painting has to be done on a wet wall, whereas he wanted to work slowly on the painting with the sufficient time to develop the greater details, he experimented a new method (from 1494 to 1498). This choice proved incompatible with the humidity of the exterior wall, which accelerated its deterioration.
In order to try to save the painting, numerous restoration methods have been used, the last one being completed in 1999: this one lasted twenty years and revealed what remains of the original painting. In 1980 it was included in the UNESCO World Heritage sites list. All viewings are limited to 15 minutes, with a maximum of thirty people allowed in the room at once; the access to it is from the square in front of Santa Maria delle Grazie, on the left of the main entrance of the church.