There is the fact that an existing drawing by Peruzzi of the Crypta Balbi is the same plan used by Piranesi in delineating the Porticus Philippi within the Ichnographia.
Pictorial Dictionary notes
Crypta Balbi: there is a drawing of the Crypta Balbi by Peruzzi in the Uffizi that Piranesi copied to draw the Porticus Philippi which is in front of the Theater Balbi, and in turn Piranesi labels a long plan to the side of the theater as the Crypta Balbi.
I finally researched the battle of Philippi; it was the site of a decisive battle in the Roman Civil War after the assasination of Julius Ceasar. [The Porticus Philippi in Rome, however, has nothing to do with the battle of Philippi.] That Piranesi intentionally [mis]places this portico along the Triumphal Way is therefore appropriate. Augustus Ceasar, the first emperor, is the one who benefitted most from the victory at Philippi.
There is also a strong Christian connection to the city of Philippi as the first Church founded by St. Paul on European soil. I see this as a major event on the Triumphal Way in reverse. There is also the quotation (Philippians 3:20) "But our citizenship is in heaven from which also we eagerly await a Savior, our Lord Jesus Christ. ..." Later scholars apply this quotation to St. Augustine's The City of God. Perhaps the Ichnographia is "the city of God" in negative/spiritual form.
...researched Gaius Flaminius because Piranesi's inversion of the Circus Flaminius within the Ichnographia. It turns out that Flaminius did go against the grain of the Senate and was of plebeian background. Sue Dixon also mentioned that Piranesi uses Flaminius as a point of subdivision in his Il Campo Marzio text of the districts history, (Piranesi actually thinks highly of Flaminius and his circus), and she (Sue) noted how the via Flaminia is not correctly delineated within the Ichnographia--the circus and the road were built by the same man. Perhaps Piranesi chose to delineate both these entities incorrectly to accentuate that Flaminius, in going against the grain, began a new effect on the land use of the Campo Marzio--thus showing the circus rotated 90 degrees in order to make it stand out. As for the Via Flaminia, there is no immediate explanation as to why it meanders off into a totally wrong direction, but it is worth noting the many plebeian homes that Piranesi situates along the street; this may be a reference to Flaminius' own plebeian background.
There is also the area called Prata Flaminia (within which the Porticus Philippi is situated) and I'm not sure if Flaminius also donated this land to the city/citizens.
Porticus Philippi (Portico di Filippo) «Ovid. nel lib. 5, epig. 50, Sesto Rufo, e P. Vittore nella Reg. IX di Roma.»Ve ne rimangono le rovine, che si dinotano nella Tavola 2, col num. 5, e nella 3 e suo indice col num. 60, e si dimostrano in prospettiva nella Tav. XXIV. see chapter 5, article 14.
built 29 BC
In 29 B.C. L. Marcius Philippus restored the temple and built a colonnade, the porticus Phillippi round it. This composite structure is mentioned as late as the fourth century, and some remains have been found in the piazza Mattei. . . .
The porticus Philippi, built as the porticus of the temple of Hercules and the Muses, by L. Marcius Philippus, the stepfather of Augustus, at the same time that he rebuilt the temple. The exact date is not known. This porticus is represented on the Marble Plan, and is mentioned in the fourth century. It contained some famous pictures, and hairdressers' shops. A few of its ruins have been found in the piazza Mattei. (Platner)
Porticus Philippi. The above-mentioned fragment of the marble plan which is inscribed AEDIS . HERCVLIS . MVSAR(VM) does not show the temple itself, butonly a part of its surrounding porticus or quadrangular colonnade, which was added by L. Marcius Philippus, the stepfather of Augustus, who also rebuilt the temple itself; see Suet. Augustus 29; Martial, v.49,12; and Ovid, Fast. vi. 799. Pliny (Hist. Nat. xxxv. 114) calls this enclosure the Porticus Philippi, and says that in it were three pictures by the Graeco-Egyptian painter Antiphilus-Liber Pater, Alexander the Great as a boy, and the death of Hippolytus when his horses were frightened by the bull sent by Posidon.
Very little remains of these buildings now visible, but some portions of the walls were discovered during the demolition of the old street to the north-west of the Porticus Octaviae. (Middleton)
. . . in the portico of Philippus ladies could find the latest fashions in wigs and hairdressing that the fancy of Roman coiffeurs could contrive. (Lanciani)
life, death, and the triumphal way [inversion]
I spoke with Sue Dixon yesterday and told her of my latest "discoveries" regarding the life and death axes of the Ichnographia, the arch of Theodosius et al and the further symbolism of the Porticus Neronianae as an inverted basilica-cross. She too became excited by my discoveries and then also brought further insight, especially in reference to the issue of the papacy and its research during the eighteenth century into the early Christian Church. She spoke of Bianchini and his nephew (a contemporary of Piranesi's) and their dual volumes of pagan (Roman) and Christian art, and she also mentioned how the papacy of the eighteenth century had lost (more or less by force and financial restraints) much of its political power and thus took on a very pious role--exhibiting not its worldly power but its almost mystical or spiritual power.
What I was saying about the apparent Pagan-Christian conversion-inversion narrative of the Ichnographia fit with what research Sue is continually doing regarding the contemporary and early eighteenth century influences on Piranesi and the whole issue of proto-archeology - history of the eighteenth century.
After speaking with Sue, I began thinking of the significance of the arch to the victory over Judea that is situated to the western end of the Bustum Hadriani. I now see it related to the pagan-Christian conversion-inversion of Rome, but in terms of Roman history it is a somewhat marginal issue-event. Yet, in terms of Christianity, the Roman victory over Judea, and hence the fall of Jerusalem, is a significant, albeit still sorrowful, event because of this event's relationship, and indeed verification of certain-particular passages of New Testament Scripture, i.e., Jesus' answering the Apostles question of when Jerusalem would end (which I think is in Mark or the Acts of the Apostles). Seeing how a seemingly minor event in Roman (Imperial) history can at the same time be a critical event for the foundation of Christianity made me think about how the Roman Judaic victory unwittingly gave manifest confirmation that Christianity had from that point forward absorbed Judaism.
Although it comes from the margin or edge, the significance of the victory of Judea arch sheds a major light upon the narrative Piranesi tells--Piranesi's "story" is about Christianity's similar absorption and concomitant destruction of paganism. This notion of Christianity absorbing both Judaism and paganism has major theological implications, especially with regard to a heretofore perhaps ignored importance-significance of Rome and the Roman Empire within the Canon and doctrine of the Christian (Catholic) faith.
...the real axis of St. Peter's Basilica and Square. This axis is fundamental to Piranesi' axis of life--and the most significant point alone the existing axis is the burial place of St. Peter, which, although not noted in the Ichnographia, is nonetheless an ancient Roman artifact.
...the story of the Triumphal Way. ...follow the triumphal path on the plan, and explain the entire route in Roman-pagan-triumphal ritual terms. ...bring up the essential concept of reenactment, the reenactment that Piranesi here designed, especially the well planned sequence of stadia and theaters along the way. Piranesi made use of what was actually once there.
When the route reaches the wall at the Temple of Janus, attention turns to Triumphal Arch-Gate, which is closed during the years of inactivity. Does the Triumphal Way then bounce off the wall and go back the way it came? Does the Temple of Janus allow us to go in either direction? (Other clues of inversion abound: obelisk in the Horti Salustiani, Porticus Phillippi, the Arches along the Via Lata, the Via Flaminia, the Circus Flaminia, the obelisks at Augustus's Tomb. The recurring inversion theme points to a greater meaning/symbolism.) The Temple (arch) of Janus represents the Arch of Janus built by Constantine (who might himself be called the Janus figure of Christianity) and this is the initiation of the way of Christianity's triumph: the profane to the sacred; the forest, hell, purgatory, heaven; the path of salvation through Christ and the Church.)
...the way from the profane to the sacred ends at the Area-Templum Martis as symbolic of the union of the most sacred site ancient Rome (or at least its point of origin) with the most sacred site of Christian Rome (St. Peter's place of burial) and also the point of origin of Christian Rome.
The garden of Nero is the ultimate field of inversion: Horti Neroniani to Vatican City, the garden of antichrist to the Church as the Body of Christ, the foremost seat of the Church of Christ, and finally St. Peter's inverted crucifixion begins the conversion of Rome.
I will conclude the inversion from pagan to Christian story-line by returning to the axis of death and the Arch of Theodosius et al at its tip, and thus when compared with the intercourse building we have depicted the beginning and the end of pagan Rome. To this I will add the Jewish Victory monument and end with the notion that Piranesi has here used architectural plans and urban design to tell the "history" of ancient Rome, however, one has in a sense read both the "positive" and the "negative" image-plan -- a story where the first half is the reciprocal of the second half (and vice versa). (I am oddly reminded here of the double theaters story from Circle and Oval in St. Peter's Square.)
Pagan - Christian - Triumphal Way