This view displays the full range of Piranesi’s etching technique: the mathematical precision of perspective, extreme limits of light and shadow, and theatrical scena per angolo. Piranesi’s use of chiaroscuro reflects the baroque drama of Francesco Borromini’s design of the Basilica’s interior. Sculptures of the apostles break away from their niches as though to speak with the pilgrims below, and the torsion of their bodies and dark shadows of the folds in their draperies make them seem alive. In the foreground on the right, the distortion of scale between the colossal sculpture of Matthew and the kneeling figure below is astonishing. The figure barely reaches the lowest plinth of the fluted pilaster above. The robust volume and rigidity of the nave’s architecture recall Piranesi’s interior view of Santa Maria Maggiore, but the tone is considerably darker and more theatrical. The circular shadows from the side aisle windows create strange blotches on the pavement, which contrast with the strict regularity of the pilasters and square coffers of the roof. The lighter areas of the floor reveal the shallow lines of the transversals, which create the optical illusion of a coherent and unified space. This effect is enhanced by the sparsely populated interior, which focuses viewers’ attention on the architecture. However, there is one figure that commands our attention. Beside the fluttering scrolls of the caption, a well-dressed man in a haughty pose looks out at viewers. His open stance and direct gaze invite them inside the interior as though he were a cicerone or an actor. Indeed, Piranesi’s combination of oblique perspective, the precise mathematical grid of the floor, and the rich ornamentation of the nave evokes the famous stage designs of the Bibiena family (see below). 
Similar to Bibiena's perspectival projection, the rigid lines of the pavement contrast with the sumptuous curves of the niches and elaborate reliefs of the entablature. These theatrical elements of the composition also serve to distinguish between the multiple architectural styles of the church, singling out Borromini’s seventeenth-century design. The monumentality of the tall pilasters and wide arches of the nave appear almost restrained compared to the gothic spires and lattice work of the medieval ciborium, gilded coffered ceiling, and sparkling mosaics in the apse. While perspective creates spatial coherence, it also calls attention to the disjointed nature of the architecture which endured multiple restorations over the centuries. Around 1763 Pope Clement XIII Rezzonico put out a call for the renovation of the apse, choir, and aisles to be based on Borromini’s initial design. According to letters of the time, Piranesi was favored for the job, as the Pope had highly praised his presentation drawings, one of which appears below (Sørenson 172).  
During this time, however, the renowned architect Luigi Vanvitelli remarked that if Piranesi were indeed chosen, Romans would “see what would come out of a madman’s head” and that “no one wants a lunatic to complete the tribune at San Giovanni in Laterano, even though Borromini, who restored the church, was not particularly level-headed” (cited in Sørenson, 172). The Pope ultimately chose another architect, but, for unknown reasons, the project was abandoned soon thereafter. Piranesi’s interior view of the Basilica was probably produced around the time of this commission in the 1760s. This view’s heightened juxtaposition of different architectural styles reflects the combination of fantasy, design, and mathematical perspective in Piranesi’s architectural practice. (ZL)

To see this image in the Vedute di Roma, volume 16 of Piranesi’s Opere, click here.