gleamandglare:

Haltadefinizione, or “HAL9000″ (English version here), an Italian project specializing in high-definition photography, has made available on the web several great masterpieces in what can be considered extreme high resolution.

So far, there are ten works viewable on the site:
Da Vinci’s Last Supper
Da Vinci’s Annunciation
Botticelli’s The Birth of Venus
Verrocchio & Leonardo’s The Baptism of Christ
Gaudenzio Ferrari’s Life Stories of Christ
Pontormo’s Deposition
Agnolo Bronzino’s Elanor of Toledo
Francesco Paolo Michetti’s The Daughter of Iorio
Caravaggio’s Bacchus