Piranesi agreed with both Palladio and contemporary authors on certain key points: first, that the main structure was composed of two large hemicircular chambers used in either summer or winter (as described in annotations “1” and “2”), second, that the vaults of these chambers were decorated with stucco in a diamond and square pattern (seen in the central arch and in the upper story below “2”), and, finally, that sculptures of “illustrious men” occupied niches throughout the building. In addition to the textual references to Palladio’s treatise in the key, Piranesi visually alludes to the second plate of the monument, which shows the ornamental reliefs of the upper vault in detail. Tempering a bold claim with an established visual source, while ultimately correcting or disproving that source, was typical of Piranesi’s approach to argumentation.
Piranesi cites archeological and geographical evidence to support his claims, which he first elaborates in the Antichità Romane. Piranesi asserts that observations made by “modern writers” have not sufficiently “considered the form of the ruins, which would have been enough to dissuade them from their suppositions [I moderni Scrittori suppongono ... senz' averne considerata la forma, la quale sarebbe bastata a ricredergli dalle loro supposizioni]" (Index to the "Pianta di Roma" Antichità Romane volume I, no. 284). The assumption of his contemporaries that any sort of apse or hemicycle would automatically indicate a temple demonstrates just how “little knowledge” [poca scienza] they have of Roman architecture (ibid., no. 284). Anyone with the most basic understanding of domestic architecture, he continues, would know that virtually all Roman buildings have such features. The hallmarks of ancient Temples, such as a portico or pronaos (evident, for example, in the Pantheon), Piranesi demonstrates, are notably absent.
In addition to the formal features of the ruins, Piranesi argues that their geographical location, adjacent to the main hall of the Domus Aurea and the Colosseum, supports his revision of previous authors. Piranesi further elaborates this argument in his reconstruction of the Roman Forum (see the entire map here, detail below).
The print seen above corresponds to number 62, while the main complex of the Golden House of Nero is indicated at 57 and 58. The light hatching indicates Piranesi’s conjectural plan of the buildings, while the darker shading indicates the extant ruins. The topographical reconstruction of the Golden House, in tandem with the visual evidence provided in the three engravings of the structure in the Vedute di Roma, prove Piranesi's argument that this particular ruin was a natural extension of the domestic complex built by Nero (Wilton-Ely 1978, 52). It should be noted that contemporaries did not agree with Piranesi’s assessment, and the building was considered to be the Temple of the Sun until only recently and has now been identified as the Temple of Venus and Roma. However, Piranesi’s revisions show his willingness to challenge scholarly authorities and, moreover, the ways that the textual and visual elements of the Vedute di Roma, which were aimed at tourists, featured in his broader archaeological arguments, written for a different audience, across the entirety of his œuvre. (ZL)
To see this image in the Vedute di Roma, volume 17 of Piranesi’s Opere,