Among the numerous projects commissioned by pope Nicholas III Orsini (1277—1280), the design and decoration of the chapel of San Lorenzo at San Giovanni in Laterano, known as the Sancta Sanctorum, signaled a new direction in papal patronage. Unlike the projects of his predecessors, which celebrated the office of the papacy rather than the person of the pope, the decoration of the Sancta Sanctorum emphasized the quasi-Imperial romanitas, or Roman lineage and authority, of Nicholas himself, marking a new emphasis upon personal and familial aggrandizement that prefigured trends in later papal patronage.

One fresco in particular, the Crucifixion of St. Peter, should be recognized as the earliest topographically specific view of Rome, depicting Orsini-occupied monuments in a Roma Ursina dominated by Nicholas III and his family. Through close examination of topographical, historical, and literary sources, the present study presents new identifications of several of the monuments in the fresco, correcting a longstanding error regarding the identity of the obelisk in the scene.

Finally, it demonstrates that this fresco established the rhetorical and pictorial topoi for subsequent Petrine crucifixion scenes, including those of Giotto, Cimabue, Deodati Orlandi, and Jacopo di Cione.