In contrast to the seclusion of plate XII, here we see much more dynamism and movement. Several human figures populate this plate in busy and even joyous affairs: they gesture and point to the architecture with excitement and purpose, as opposed to the desperation seen in plates II, V, and VI.
Piranesi recaptures the subject of the religious festivals and processions but, this time, he focuses more specifically on the preparation of the city of Rome for these events through the depiction of ladders, beams, scaffolds, pulleys, and cranes. The preparatory work transformed the profile of the city, displaying a myriad of devices used to set up the structures and ornate the city. Many of the mechanical tools to lift elements such as panels and banners used for the festivities are scattered throughout the plates of the Imaginary Prisons. Wooden beams tied to each other, so conspicuously visible in the Carceri, resembles the technique of joining beams developed by Nicola Zabaglia (1664-1750), as Francesco Rostagni (b. circa 1740) recorded in engravings. Piranesi also addressed the preparation of the city for the festivals through the many cloths that tiny human figures hang on the parapets of bridges and catwalks in several plates. They allude to the textile ornamentations hung on windowsills, such as tapestries and flags. Piranesi also makes reference to the magnificent fireworks typical of the Chinea in the mysterious clouds of smoke in the Carceri. This awe-inspiring feature was truly a high point during the ceremonies.
The religious festivals involved a huge industry that, in turn, offered job opportunities for many artists and architects. A great apparatus was necessary to enable these events. The focal point of the possesso, for instance, was an ephemeral triumphal arch. Likewise, the main feature of the Chinea was a colossal mobile structure, called macchina, to which fireworks were attached. Many engravings of the epoch, used to publicize the events, documented the macchine and other ephemeral structures with their profusion of baroque ornamentation.
The aesthetic choices for these events and the combined sponsorship of the Catholic Church and European monarchy must have infuriated Piranesi. His criticism is evident in the illustrations of the Imaginary Prisons. In this plate, for instance, he represents an abandoned well and fragments of a trestle on the foreground. Whereas the well represents the source for inspiration grounded on the legacy of the ancient Romans largely disregarded by the human figures depicted in this plate, the broken trestle, implying the idea of a shattered bridge, symbolizes the lack of continuity between the glorious classical past and Piranesi’s contemporaries.