The drawing's pencil framing lines suggest it was a finished composition rather than a sketch; a similar framing line appears in Adam vol.57/22, another drawing of the aqueduct at Tivoli. This is an almost identical view to that in Paoli, Avanzi Delle Antichita Esistenti a Pozzuoli Cuma e Baja, Naples, 1768, pl.IX after a drawing by Giovanni Battista Natali. The description given for pl.IX makes it clear that the square form became a cylinder, which 'terminava forse in una cupola' [possibly terminated in a cupola] and this is shown in Adam vol.57/16 and 57/21. This view may also be compared with a similar drawing of the interior of the Temple of Mercury by Hubert Robert who visited the site in April 1760, an engraving of which is in Abbé de Saint-Non, Voyage Pittoresque en Sicile et Naples, Paris, 1781-6, vol.I, part 2, opp. p.212 (see C. Denison et al, Exploring Rome: Piranesi and His Contemporaries, Cambridge, Massachusetts and London, 1993, p.178). At least two other views of the Temple were made by Clérisseau, a worked-up gouache of which is in the Pierpont Morgan Library, New York (see Denison, 1993, op. cit., p.157); they may have been made in either 1755 or 1761. Adam's view is the duller version, although it is the more topographically accurate.
The fact that this sheet contains drawings of sites in both Rome and Naples appearing on the same piece of paper is indicative of Robert Adam's economical use of paper.