The entrance to the former refectory where Leonardo's famous masterpiece "Il Cenacolo" the Last Supper can be admired is beside the façade and main entrance of the Church of Santa Maria delle Grazie. The realization of the fresco of the Last Supper was part of the large scale artistic and cultural renewal that took place in Milan from 1490 onwards under the patronage of Lodovico il Moro. Santa Maria delle Grazie played an important part in this movement. In 1495 while Donato Montorfano was finishing his painting of the Crucifixion in the refectory Leonardo received a commission from the Duke to decorate the wall opposite with the Last Supper. The four lunettes above the fresco are decorated with vegetable garlands around coats of arms and contain the names of Lodovico, Beatrice and their children and document the relationship. Work on the Last Supper proceeded slowly notwithstanding the entreaties of the Duke and Prior. It took Leonardo almost four years to finish the painting (1494-1498) using a "tempera forte" tecnique as if he was working on a large panel (4,60x8,80m.). His first unusual decision was not to use the well-established fresco technique which offered better guarantees for the preservation of the painting but imposed a strict time limit on the artist. He preferred maximum liberty while working on a project in order to correct, modify and obtain special chromatic effects. His eccentric temperament meant that he was subject to alternating bursts of activity and complete repose as is testified by Matteo Bandello's account while he was a guest of the Monks at the monastery and often saw him at work. The "Cenacolo" was a theme frequently portrayed in monastery refectories but Leonardo's Last Supper was very innovative. Not only did it radically modify the layout of the scene but also depicts the evangelical episode with impressive realism. The episode, described in the gospels, represents the dramatic moment in which Christ announces that one of his Apostles will betray him. The scene is lit up by a slanting ray of light crossing the table, illuminating the right hand wall reappearing against the landscape glimpsed through the three doors in the background. In the centre, apparently isolated from the agitated apostles surrounding him is the figure of Jesus Christ. The Apostles are depicted in groups of three, each one is gesturing showing his subjective reaction to the emotion stirred up by Christ's dramatic announcement. The painting is also exceptional for the play of perspective which makes the supper area appear longer until it merges into the distant landscape. Recent restoration work was begun in 1978 and finished in 1999 the experts made every possible effort to recuperate Leonardo's original painting which had been completely altered by previous interventions. Numerous problems had to be faced: some regarding the aesthetical aspect and others concerning the creation of a suitable environment to protect the wall painting from future deterioration caused by dust, vapours, fumes and damp. To achieve this aim a sophisticated system of air filters preventing polluting substances from reaching and accumulating in the protected Refectory area was installed. Two Milanese institutional bodies shared responsibility for the preservation of the Last Supper: the "Soprintendenza per i Beni Architettonici e il Paesaggio di Milano" resolved the delicate environmental problems and set up the museum while the "Patrimonio Storico Artistico e Demoetnoantropologico" office organized stripping and restoring the painted fresco Both government supervisory bodies worked in close collaboration with the "Istituto Centrale del Restauro" and with specialized foreign institutions doing their utmost to make use of the most up to date research and tools available in the field of scientific culture in this field.