The so-called New Fresco, discovered in 1980 beneath a layer of plaster in the main hall of Siena's Palazzo Pubblico, is one of the most puzzling works in the canon of medieval art. The difficulties inherent in trying to comprehend an image that bears no inscription and no regular iconography are exacerbated by the fact that, ever since its discovery the New Fresco has been embroiled in the notorious dispute over the Guidoriccio fresco, which sits on the wall above.

This article, which considers the New Fresco in isolation from the Guidoriccio debate, aims to elucidate the painting's subject via three methods of study that have yet to be adequately explored. First, the implications of the form and imagery of the fresco are analysed independently of any contextual information, yielding the provisional conclusion that it represents a treaty between Siena and members of the local aristocracy. Secondly, the picture is compared with near-contemporary Italian images that employ similar pictorial strategies and address similar subjects, so as to elucidate the way in which the imagery operates. Thirdly, detailed topographical evidence is used to identify the town in the painting as Santa Fiora, the feudal seat of the famous Aldobrandeschi counts.

Concluding that the New Fresco should be renamed The Treaty with the House of Santa Fiora, the article ends with some brief reflections on the artist's ambitious attempt to represent his subject without obvious reference to the verbal culture in which 14th-century Siena was immersed.