Piranesi’s purpose in studying ancient remains, as he explained in the Preface of Le Antichità Romane, was to “conservarli col mezzo delle stampe” (1). This purpose is especially effective for what remains of the Roman waterways that were already in Piranesi’s age increasingly swallowed by the growing modern city. Thanks to his views and demonstrations in the technical plates, we have glimpses of what was lost. 

This view shows, and the key details, the aspect that the final castello of the Claudia aqueduct (C) had in the eighteenth century, with what remained of its arches (A) and their upper speco (B) from which water ran through the Neronian aqueduct's channels. The nervous, interrupted, frothy lines of Piranesi’s style, furrowing the ruined masonry, characterise the structure, which is covered by vegetation. The modern building, just like the vegetation, also seems to be climbing to the castello’s ruins; it is an unpretentious construction with a haphazard appearance, a makeshift dwelling lacking, for Piranesi’s eyes, any architectural interest. If it weren’t for the staffage figures he included in the customarily hectic and bustling plate, we could hear the silence of a deserted place where the magnificence of ancient times has been lost. 

The contrast between bright light and deep shade is underlined by the various tones of deep blacks Piranesi achieved in depicting the arches and the ruined elements in front of them. These effects are obtained by the technical mastery he reached in controlling every single step of etching, by modulating the chiaroscuro thanks to different furrow depths obtained by successive acid bitings and final burin retouchings.  

The site, which is marked with no. 184 in the Map of Rome, is described in the Index to the Map of Rome, where Piranesi explains, referring to Frontinus’ De aquis urbis Romae, that the Acqua Claudia was diverted from Porta Maggiore over the Neronian Arches to reach the Caelian Hill and, and from there, both the Aventine and the Palatine Hills. It is possible to  follow the route in the Topographical Map of the Roman Aqueducts: from Porta Maggiore (16), where the Monument of the Fountainhead of the Acqua Claudia and Anione Nuovo stood, the Neronian Arches arrived next to the Archway of the Consuls Dolabella and Silanus, where they branched off (33) and then, following the pipeline (34-37), ran to the terminal castello on the Aventine Hill (37). 

Here, as Piranesi indicates both in the Index to the Map of Rome and in the etching’s key, under the modern building depicted in the view there lean the ruins of the castello and the “rovine del Castello e de’ bagni privati di Trajano.” These can be most likely identified with the so-called Terme Surane, a private thermal complex which got its name from senator and consul Lucius Licinius Sura (40 - circa 108 AD), a close friend of Trajan. They appear in one of the fragments of the Forma Urbis Romae (no. 39 in close-up below) which Piranesi included in the Map of Rome, where he interpreted the incomplete inscription as: “39 BAL SVRAE) BALneum SVRAE. Bagno sull'Aventino nella Casa di L. Sura, il quale fu Console sotto Nerva Imp.re.” 
His reconstruction was later confirmed in the studies carried out by Giuseppe Gatteschi (1866-1935) in the early twentieth century; in his plan of the Aventine Hill, the Claudian castello and its final arches are placed on the north side of the baths (indicated as Archi della Claudia, below).  
This proves once again Piranesi’s contribution to preserve memory of the ancient places; his etchings and studies, as it turned out, were fundamental for later archeologic research. (CS)