Altarpiece (detail)
by GUIDO DA SIENA, Tempera on wood
The left panel of the altarpiece depicts the Transfiguration. The feast of the Transfiguration (6 August) was not celebrated by the medieval Latin church and is therefore not often shown in early Italian painting. This panel is one of the two rare examples, the other being the very damaged thirteenth-century fresco on the east wall of the north transept in the Upper Church of San Francesco, Assisi.