 The opposite wall of the refectory is covered by the Crucifixion fresco by Giovanni Donato da Montorfano, to which Leonardo added figures of the Sforza family in tempera; these figures have deteriorated in much the same way as has "The Last Supper".Leonardo worked on "The Last Supper" from about 1495 to 1498, but did not work it continuously.The beginning date is not certain, as the archives of the convent for the period have been destroyed.