Plate IV
Even though Piranesi had already shily depicted marches in Plate III and in the title page, it is in this plate that Piranesi makes the scene very prominent in the compositional scheme of the illustration. The darkened archway in the forefront frames the arcade on which the march takes place, right in the center of the pictorial space. The relief portraying battle scenes introduces the idea of the triumphal marches of the classical past, a reference that Piranesi profusely utilizes throughout not only the Carceri series but also other works, like in La Magnificenza ed Archittetura de' Romani, represented by symbolic objects such as trophies, pieces of ancient Roman military apparel, shields, swords, laurel wreaths, and so on.
Piranesi, nonetheless, uses the powerful imagery of the triumphal marches as commentaries for the role of the Catholic Church in his own time. The church, emulating the Roman tradition of "bread and circus," offered many public pompous festivals to commemorate a wide range of events. They often combined ephemeral structures with fireworks and musical performances to create a strong impression on the populace. In the Carceri, Piranesi evokes these religious festivals to criticize the Catholic Church’s affiliation with the monarchy. Among the most important festivals in Piranesi's time was the Lateran possesso and the annual Chinea, both patronized by the aristocracy. The possesso consisted in the walk of the newly elected pope to the basilica of St. John Lateran, over which Popes traditionally presided as Bishops of Rome. Considering that Piranesi first moved to Rome in 1740, he may had witnessed the possesso of Pope Benedict XIV (papacy 1740 – 1758) and certainly witnessed the possesso of the Venetian Pope Clement XIII (papacy 1758 – 1769). The Duke of Parma ( from the well-known Farnese family) was responsible for the possessi, and the Kingdom of Naples, for the Chinea.
As representations of the conjunction of the power of monarchy and the Catholic Church, the festivals reproduced the standards of taste of the two institutions, strongly committed to the maintenance of late Baroque and Absolutism. Severely hostile to both, Piranesi portrays the festivals as elements that "imprison" the imagination and the good taste and, at the same time, entraps them in the kaleidoscopic agony of the prisons.
In comparison to the first state, Piranesi considerably reworked this plate. He not only increased the number of structures along the march, but also added many elements in the foreground, such as wheels, spikes, beams, bollards and chains. Piranesi blocks the opening under the archway, inviting his audience to decline the march and, instead, continue the voyage into the subterranean.