Plan, elevation and section engraved by Piranesi, with Figures I to IV keyed to Italian notes.
Source: Piranesi Archit. dis. inc., old map, public domain
This engraving from Piranesi's architectural drawings combines a ground plan, a front view and a cross-section of the portico, each numbered as a figure with Italian notes. It records how the structure looked to an eighteenth-century draughtsman.