As Piranesi describes (in the Index to the Map of  Rome and in the Explanation of the Map of the Aqueducts) and depicts (in the linked images), the Neronian Arches ran from Porta Maggiore to bring water from the Claudian aqueduct to the Caelian Hill and, from there, to the Palatine, for its imperial palaces, nymphaea and fountains, and to the Aventine Hills, where the terminal storage of the Castello dell’Acqua Claudia stood.

The arches reproduced in this view are marked with no. 209 in the Map of Rome and its related Index; in the Topographical Map of the Roman Aqueducts, this stretch corresponds to the one comprised between the branch marked with no. 33 (moving towards the Aventine Hill) and the terminal water reservoir which supplied the Caelian Hill (no. 38). Piranesi chose the view from the Caelian toward the Church of Santo Stefano Rotondo, placing what remained of the castello’s fistulas and cloacae (B and C in the etching’s key) in the right of the image. On the far left, instead, at the end of the long perspective view of the arches, he omitted the Archway of Dolabella and Silano, the subject of another plate, in which, instead, the Neronian Arches are visible through the archway.

Additionally, he made a distortion in perspective and included, in a sort of wide-angle fisheye view that straightens natural vision, the façade of a church that can be assumed to be Santa Maria in Domnica, even though it lacks the porch that characterises its aspect. The church is actually located behind the bend of the Archway of Dolabella and, therefore, was not visible from the point of view adopted for the etching. This is the only hint of contemporary Rome in the scene. Moreover, perhaps to underline the continuity of the arches that were no longer standing in his time and to let his viewers imagine their ideal procession, Piranesi included the single surviving pillar still standing in Piazza della Navicella. The pillar, a kind of landmark, is present in other views, such as the one included in Giuseppe Vasi’s Delle Magnificenze di Roma Antica e Moderna (1747-1761) or the one published by Piranesi (below, left) in the series Varie Vedute di Roma Antica, e Moderna disegnate e intagliate da celebri autori (1745-48). In the same series, Piranesi represented another stretch of the Neronian Arches (below, right), that is next to the courtyard of Santo Stefano Rotondo (Map of Rome, no. 212).
Piranesi’s visual techniques create striking effects. The bright light which invades the scene and the darker parts which, in shade, gain depth, produce the strong contrast of chiaroscuro. The human figures, which diminish in size towards the vanishing point, primarily emphasize the huge dimensions of architecture. This effect is enhanced by the perspective construction, with the repetition of the same element, the arch, in a continuum that gives a sense of bewilderment and vertigo and, thus, fascinates the observer. These feelings, which invoke the contemporary theory of the sublime, are amplified by repetition, distortions of perspective, exaggerated dimensions, and the strong contrast of chiaroscuro. (CS)