You may wish to learn more about the creation of this archaeological area first.
The area in May 2020 seen from Via Florida (thus named after Cantacuzina Floridi, a noblewoman from Cyprus who lived there in ca 1500) at its southern end
The Corso Vittorio Emanuele reaches the Largo di Torre Argentina, usually known as Largo Argentina. On the left of this open space is a group of Four Republican Temples, excavated in 1926-1935 (entrance, usually closed, in Via di San Nicola dei Cesarini, on the E side; for adm. apply at Piazzale Caffarelli 3), an area which abounds in cats.
Blue Guide - Rome and Environs - 1979
The area contains a row of four temples of medium size, more or less aligned, but without other clear relationship. Because of the location where they stand, between Pons Triumphalis and the Capitol it is presumed they are on the line of the beginning of most, if not all, triumphal processions. The two northernmost of the temples were always known, remains of the northernmost, known as Temple A, having been built into the fabric of the church of S. Nicola dei Cesarini, while a few columns of the circular temple next to it, Temple B, could be seen in a courtyard next door.
As of June 2023 the area, which belongs to the City of Rome, is open on an ordinary basis and some of the statues, inscriptions, altars which were found during the excavations are on display in a small gallery. Visitors cannot directly access the temples, but walkways allow them to see the ruins up close.
The identity of the divinities to whom the temples were dedicated is very much disputed and several hypotheses have been put forward, but there is no firm evidence because many deities are known to have had temples in the Campus Martius. The temples therefore are usually identified by a letter starting with that at the northern end of the area which was the first to be excavated.
Tufa (tuff) may be found used in many existing monuments of ancient Rome, such as the drains of the middle and southern basin of the left bank, the channels and arches of the Marcia and Anio vetus, the Servian walls, the temples of Fortuna Virilis, of Hercules Magnus Custos (Temple B), the Rostra, the embankment of the Tiber, etc.
Rodolfo Lanciani - The ruins and excavations of ancient Rome - 1897
The oldest of the temples is probably Temple A, because its original structure was built with tufa from Grotta Oscura, a quarry which was first used by the inhabitants of Veii and, after the 396 BC conquest of the town, by the Romans. The quarry was located near a stream which emptied into the River Tiber and its stones could be easily carried to Rome. In the second half of the IInd century BC the Romans began to exploit the quarries of Monteverde. Temple A stood on a high tufa podium with 4 columns on the front, which was accessed via a staircase of 18 steps. Probably after a catastrophic flood in the IInd century BC, the floor of the entire area rose and an extensive Monteverde tufa platform was built in front of temples A and C. In the second half of the Ist century BC the sacred building was incorporated into a larger temple, with 6 columns on the front and 9 on the long sides. Numerous restorations were carried out in the following centuries, among which those of the Severian emperors were particularly important.
Temple B (see another view of it in the historical section)
There is a verse in Ovid which mentions a temple of Hercules, the special guardian of the Circus Flaminius. The poet further intimates that this temple was dedicated in the time of Sylla, near the church of S. Nicolo de' Cesarini. In the yard of the convent of the Padri Sommaschi there are some remains of a temple, which do not ill correspond to all these circumstances. It is situated at no great distance from where the Carceres of the Flaminian Circus may be supposed to have reached: it is round, as the temples of Hercules usually were; and the material of which it is built characterises it as a work of the republic. It is true, as far as the vicinity of the Circus furnishes an argument, there are many other temples to contest the title, but none of them have so many coincidences, however slight they be, as the temple of Hercules Custos.
Richard Burgess - The topography and antiquities of Rome - 1831
Templum Herculis Magni Custodis ad Circum Flaminium (Temple of Hercules, the great keeper of the Circus Flaminius). - In the garden of the small cloisters annexed to the church of S. Nicolo ai Cesarini there are remains of a circular temple with fluted columns of tufa coated with white plaster, and resting upon a basement of travertine. The church itself rests on the foundations of another temple, rectangular in shape, and built likewise of tufa coated with stucco. Both appear in fragment xvi of the "Forma Urbis". Three or four hundred years ago they were in a much better state of preservation. The round temple was named "Veneris in Calcarario," "calcararium" meaning the region of the lime-kilns and of lime-burners, which extended from S. Lucia dei Ginnasi to the church of the Stimmate, once called of SS. Quaranta in Calcarari. The name, however, was wrong: the elegant little structure belongs to Hercules the protector of the circus, to Hercules the oracular god, so much in favour with the charioteers. (..) The birthday of the god, February 1, was celebrated with races and other races were run on June 4, near the Porticus Minuciae, before a colossal bronze statue of him which is supposed to belong to this temple. Lanciani
Hercules, like Esculapius, Apollo, and the Fortune, was undoubtedly an oracular god, as shown by the existence of many temples and sanctuaries in which oracles were given in his name. Lanciani
The excavations led to the discovery of a statue of Fortune, rather than of Hercules. The statue was an acrolith (from the Greek words meaning height/extremity and stone), i.e. the head, the arms and the legs were made of marble, whereas the clothed parts of the body were made of wood or bronze. It was not a new development in sculpture because this technique had been used by Phidias at Olympia in the Vth century BC; two acroliths of Emperor Constantine in marble and bronze are on display at Musei Capitolini.
Temple B has a circular plan on a high podium preceded by a staircase; it was originally peripteral (i.e. with a perimeter of free columns), but it was transformed into pseudoperipteral at the beginning of the Ist century BC, by enlarging the cell which incorporated the 18 tufa columns. After a disastrous fire in 80 AD, the space between the columns was closed by a brick wall which was decorated with stucco pilasters.
(above) Capitals of Temple B; (below-left) relief reused in the church, now in a small gallery at the archaeological site; (below-right) a highly decorated plinth (column base) near Temple B; the image used as background for this page shows the "strigil" decoration of a marble sarcophagus in the gallery
The 18 columns of Temple B were tufa shafts with Attic bases and Corinthian capitals of travertine. The final layout of the archaeological area was aimed at highlighting the Republican age features of the temples, but some of the architectural fragments which were left near them belong to restorations made in the late Ist century AD or during the Severian age.
Temple C, although only a little younger than Temple A and very similar to it in construction, was from the beginning a much larger edifice, although the altar platform in front of it was made to conform in size to that of Temple A. It stood on a very high platform of Grotta Oscura tufa. It had 4 columns on the front and 5 on the sides and it was preceded by a staircase of 20 steps. The original exact date of the temple is not fixed, but its material and style suggest it was built in the IIIrd century BC.
Temple D is mostly preserved under the current Via Florida. It was built in cement at the beginning of the IInd century BC, larger in size than the already existing temples A and C; the front, probably equipped with 6 columns, was aligned with the other sacred buildings, while the rear side protruded about 10 m. Little is known about the original phase, since at the end of the Ist century BC the temple was completely renovated. What remains are the large concrete podium covered with travertine, and the access staircase. In many ways it is the most mysterious of the four, although a dedication to the Nymphs has been suggested. The size of cella and pronaos and the lack of evidence of columns suggest that the temple was hypaethral, i.e. roofless.
Travertine pavement of the late Ist century AD in front of Temple C (see an image of the space between Temples C and D in the historical section)
The area burned in the fire of Titus in 80 AD and was restored under Domitian (who built a stadium not far away). At that time the level of the floor was again raised and repaved with blocks of travertine, the last general rehandling of the precinct. Subsidiary structures were added from time to time that eventually came to fill most of the space between and behind the temples. These we can think of as sacristies and accommodations for the temple attendants.
Statues found during the excavations which were kept in storerooms and now are on display in the gallery of the archaeological site: (left) large head of a goddess, perhaps Feronia (late Ist century AD); (centre) large head of a goddess perhaps Diana (IInd century AD); fragment of a statue of Hercules showing his club and a lion paw (see the likely aspect of the whole statue)
Temple A is probably to be identified with that which the consul G. Lutatius Catulus built in honour of Juturna after his naval victory over the Carthaginians in 241 BC which ended the First Punic War. Other archaeologists believe the temple was dedicated to Feronia or Juno Curite.
As a matter of fact Giuseppe Marchetti Longhi, a topographer who kept a journal of the excavations, recorded the finding of a heap of fragments of marble statues which appeared to have been deliberately smashed. It is therefore possible that they did not belong to the temples in the sacred area, but to other ancient buildings and were carried there to be burnt in a lime-kiln.
Round altar with a very fine ribbon, see a famous Roman relief with a similar ribbon
Temples A and C had altars on the travertine platform before the steps leading to them. The two fragments of a round marble altar might have belonged to one of the temples or have been carried to the sacred area to be burnt. The decoration does not offer clear clues for the identification of a particular deity, but the festoon of fruit could refer to Salus Frugifera (Welfare Fruit-bearer), a Latinized name of Feronia.