This image of the Baths of Diocletian is fourth in a group of five architectural plans set against illusionistic surfaces and materials. Piranesi’s plans at the end of this volume each employ various layered media, particularly paper and stone, against a background, rendered by thin hatched lines, that shows cardinal directions. Here, atop the background is a sheet of paper displaying a scale, and on it a second, curling sheet with a carefully numbered plan. Below these three layered surfaces is a lengthy caption that identifies atria, dining rooms, gymnasia, porticoes, and vestibules. This visual arrangement frames the “severe linearity” (Yegul 118) of the thermal complex itself within Piranesi’s own linear forms of rectilinear shapes and etching lines. 

But just as the curling paper edge below the plan hints at Piranesi’s tendency to mingle illusion with objectivity, the volume sets this image within the excessively elaborate network of cross-references that Heather Hyde Minor has traced (2015, 27-39). In the Index to the Map of Rome, Piranesi notes that these baths are shown, in the View of the Remains of the Baths of Diocletian, occupied by churches and convents and, in this plan, instead, “secondo l’antica loro esistenza” [according to their ancient state] (Index to the Map of Rome, no. 249). In the veduta, the baths appear in their post-medieval state, repurposed for the Catholic church. Here, however, the extant remains are filled in with what Piranesi, as well as others (including Giovanni Battista Nolli in his large map of Rome), takes to be their absent elements, and his image recreates their original state through his use of etching techniques that cause the paper to take on darker and lighter tints of black ink. Many of Piranesi’s later images combine vedute and plans, sometimes with sections and details, within single visual fields. In this case, though, the volume’s elaborate cross-references connect the veduta and the plan in order to offer a spatially and temporally comprehensive account of the thermal complex. (JB)