One of my favorites.

Enguerrand Quarton(?), Pietà of Villeneuve-lès-Avignon, c. 1455, oil on wood, 163 x 219 cm (Musée du Louvre)

Smarthistory has mastered the format.  Concise and thorough investigations into great works of art.
More free lessons at: http://www.khanacademy.org/video?v=_0…