Temple of Janus (ca. 260 BC)

Remains of the temple of Janus in the Forum Holitorium adapted from images in this webpage by Jeff Bondono:

Left: surviving columns from the temple (to the north of the church of San Nicola in Carcere)

Right: reconstruction of the facades of the temples of Spes, Juno Sospita and Janus in relation to the present church

Plan of the remains of the temples of Spes, Juno Sospita and Janus at San Nicola in Carcere

(adapted from this page of the website Archeoroma)

According to Tacitus, in 17 AD, the Emperor Tiberius:

1. “... dedicated [a number of] temples that had been ruined by age or fire and restored by [the recently-deceased] Augustus.  These included ... Iano templum (the shrine of Janus), which had been built in the Forum Holitorium by C. Duilius, who primus rem Romanam prospere (was the first Roman to mount a successful naval campaign) and [thereby] earned a naval triumph over the Carthaginians.  [At about the same time], Germanicus [Julius Caesar, Tiberius’ nephew], dedicated the [nearby] temple of Spes, which had been vowed by A. Atilius in the same war”, (‘Annals’, 2: 49). 
   

Sabrina Amaducci et al. (referenced below, at pp. 254-5) reproduced the entries in:

1. ✴two of the surviving fasti that record the dies natalis of the temple as 17th August:
   

2. •fasti Allifani: “Port(unalia) n(efas) p(iaculum) fer(iae)/ Pọrtuno ad pontem Aemiliuṃ/ Iano ad theatrum Marcellì’; and
   

3. •fasti Vallenses: “Pọrtuno ad pontem Aemil.../ Iano ad theatrum Marcellì”; and
   

4. ✴the fasti Amiternini, which records the dies natalis of  Iano ad theatrum Marcello as 18th August.
   

This is usually taken to indicate that:

1. ✴Duilius’ temple, (like the Temple of Portunus in the nearby Forum Boarium)  was dedicated on 17th August, the day of the Portunalia; and
   

2. ✴after its Augustan restoration, Tiberius re-dedicated  it on 18th August (see, for example, Sabrina Amaducci et al., referenced below, at pp. 254-5).
   

Location

Location of the Temple of Janus in the Forum Holitorium (adapted from the Digital Map of Augustan Rome)

The information from:

1. ✴Suetonius, who placed Duilius’ temple in the Forum Holitorium; and
   

2. ✴the fasti, which placed it near the  (Augustan) theatre of Marcellus;
   

can be supplemented by the information from the Augustan grammarian M. Verrius Flaccus (as epitomised by Festus (‘De verborum significatu’, 358 L) that it was outside the Porta Carmentalis.

This indicates that it was one of the three temples that have been excavated on the site of the church of San Nicola in Carcere.  We know from Livy that

We know from Livy that, in 213 BC, Rome witnessed the outbreak of :

1. “... a dreadful fire ... that continued for two nights and a day: every thing was burnt to the ground between the Salinae and the Porta Carmentalis, including the Aequimaelium, the Vicus Jugarius and the temples of Fortuna and Mater Matuta”, (‘History of Rome’, 24: 47: 15); and
   

in 212 BC:

1. “Five commissioners were chosen to undertake the repair of the walls and towers of the City, and two boards, each consisting of three members, were selected;
   

2. ✴one to inspect the contents of the temples and to make an inventory of the offerings; [and]
   

3. ✴the other to rebuild:
   

4. •the temples of Fortuna and Mater Matuta inside the Porta Carmentalis; and
   

5. •the temple of Spes outside;
   

6. all of which had been destroyed by fire in the previous year”, (‘History of Rome’, 25: 7: 5-6). 
   

This suggests that the Temple of Spes was he closest of the three temple to the Porta Carmentalis.  Rianne (A. M.) Hermans (referenced below, at p. 94) agreed, and argued that:

1. “ ... the temple of Juno Sospita was  almost certainly located in the Forum Holitorium, where it was squeezed in between the temples of Janus and Spes, which were both older. ... Remains of the [three] temple have been identified under the church of San Nicola in Carcere, and [they were depicted] on the Forma Urbis [Roma of the 3rd century AD].  The temples were repeatedly restored, and most of the visible remains date from the 1st century AD.”
   

In other words , as Adam Ziolkowsk (referenced below, at p. 62, followed, for example, by Penelope Davies, referenced below, at p. 53 and by Dorian Borbonus, in had commentary at entry 168 of the Digital Map of Augustan Rome) asserted, the surviving sources for the location of Duilius’ Temple of Janus:

1. “... unambiguously point to the northern-most of the three temples [at San Nicola in Carcere].”
   

Augustan Restoration

[Fire of 31 BC]

In the account of his deeds that Augustus wrote in 13-14 AD in the form of a long Latin/Greek inscription for his mausoleum, he included the fact that:

“I restored 82 temples of the gods in the City as consul for the 6th time [in 28 BC]”, (‘Res Gestae’, 20:4, translated by Alison Cooley, referenced below, at p. 80).

Shrine of Janus Quirinus

Varro’s Testimony (ca. 45 BC)

Varro (after listing the gates in the Servian walls in a passage that is now lacunose) noted that:

1. “In addition, inside the walls, I see that there are [two] gates on the Palatine:
   

2. ✴the Mucionian, ... ; and
   

3. ✴the Romanulan ....
   

4. The third gate is the Ianualis, named for Janus. Et ideo (for that reason):
   

5. ✴ibi positum Iani signum (a statue of Janus was set up there); and
   

6. ✴a law was instituted by [Numa Pompilius, [traditionally the second king of Rome, reigning in 715–672 BC], as [L. Calpurnius Piso (last recorded as censor in 120 BC)] writes in his ‘Annals’, [which required] that it should always be open unless when there was no war anywhere.
   

7. Traditum est memoriae (tradition tells us) that it was closed:
   

8. ✴during Pompilius’ reign; and
   

9. ✴later, when T. Manlius was consul at the end of  the First Punic War (and it was re-opened in the same year), (“On the Latin Language’, 5: 164-5, translated by Gary Forsythe, referenced below, at p. 453, his F. 15)
   

Cicero may have relied on a now-lost passage by Varro when he recorded that:

1. “... the name [Janus is] derived from ire (to go), and hence the names iani for archways”, (‘On the Nature of the Gods’, 2: 67, translated by Henry Rackham, referenced below, at p. 189). 
   

However, Varro’s Ianualis was presumably differentiated from the other iani because of the (presumably consecrated) statue that had been set up there.

Gary Forsyth (referenced below, see, for example p. 189) argued that Varro relied on Piso for the whole of his F 15 (above). Robert Ogilvie (referenced below, at p. 93) similarly argued that:

1. “The tradition that [the Ianualis was] closed in 235 BC, ... after the First Punic War, derives at least from the historian Piso (ap. Varro, de Ling. Lat. 5. 165) and there may well have been an authentic notice of it.”
   

However, Mark Pobjoy (in Cornell T. C. (editor), referenced below, Vol. II, pp. 306-7, his F11) atrributed only the passage that I have underlined to Piso.  It seems to me that Varro’s use of the opening phrase ‘traditum est memoriae’ does indded indicate that Varro had not relied on Piso for what followed, in which case, Varro

1. ✴attributed to Piso the information that Numa had decreed that the Ianualis would be closed only in times of peace; and
   

2. ✴added that:
   

3. •the Ianualis stood inside the Servian walls; and
   

4. •it was closed throughout Numa’s reign but had then remained open for 627 years, except for a period of less that a year in the consulship of T. Manlius.
   

As Gary Forsythe pointed out (at p. pp. 187-8), the opening lines of Varro’s account have:

1. “... misled some modern scholars into thinking that all three gates  ... [were all on the Palatine.  However,  Varro’s] wording indicates that he viewed Janus’ gate in a different context from the other two.”
   

The context in question was both topographical and chronological: Varro did not locate the Ianualis on the Palatine and he therefore did not attribute its foundation to Romulus (although he clearly accepted piso’s claim that it existed at the time of Numa). 

Augustus’ Testimony (13-4 AD)

In his ‘Res Gestae’, Augustus included the fact that:

1. “Our ancestors wanted [the] Janus Quirinus to be closed when peace had been achieved by victories on land and sea throughout the whole empire of the Roman people.  Whereas:
   

2. ✴it is recorded as having been closed [only] twice before I was born [i.e., in the 609 years before Augustus’ birth in 63 BC];
   

3. ✴the Senate decreed that it should be closed three times when I was princeps [i.e., in the 45 years before Augustus’ death in 14 AD]”, (‘Res Gestae’, 13, translated by Alison Cooley, referenced below, at p. 72).
   

Augustus’ claim was that his ‘victories on land and sea throughout the whole empire of the Roman people’ had brought an unprecedented period of peace to Rome.  Suetonius (early 2nd century AD) similarly recorded that:

1. “The Janus Quirinus, which had been closed only twice before his time since the founding of the City, he closed three times in a far shorter period, having won peace on land and sea”, (‘Life of Augustus’, 22).
   

Interestingly, in the Greek version of this paragraph (see Alison Cooley, referenced below, at p. 73) Augustus:

1. ✴replaced ‘Ianum Quirinum’ with ‘Πύλην Ἐνυάλιον (Gates of War); and
   

2. ✴removed the allusion to peace ‘achieved through victory’, instead tactfully explaining to his Greek audience that:
   

3. ‘our ancestors ... [wanted these gates to be closed only when] all land and sea was at peace under the Romans ...’
   

First ‘Augustan’ Closure (11th January 29 BC)

According to Cassius Dio (4th century AD), before Augustus (then still known as Caesar Octavianus)  returned to Rome after his victories at Actium (2nd September 31 BC) and Alexandria (1st August 30 BC), he received many honours from the Senate, but:

1. “... the actions that pleased him more than all the decrees were:
   

2. ✴the Senate’s closing of the gates of Janus, implying that all their wars had ceased; and
   

3. ✴the taking of the augurium salutis, which had fallen into disuse at this time ...”, (‘Roman History’, 51: 20: 4).
   

The lacunose entry of the fasti Praenestini for the 11th of January (search on ‘Ianum’) reads:

‘... /ab Romulo et Ianum c...’

which is usually taken to indicate that the putative third closure of the Janus since the time of Romulus (i.e., after the closure by Numa and that in the consulship of T. Manlius) took place on 11th January 29 BC, before Octavianus returned to the City. 

Octavianus’ subsequent arrival in the City was marked by his triple triumph of 13th-15th August: according to Cassius Dio:

1. “As for the triumph:
   

2. ✴on the first day, Caesar [Octavianus] celebrated ... his victories over the Pannonians and Dalmatians, the Iapydes and their neighbours, and some Germans and Gauls [in 35-3 BC] ...;
   

3. ✴on the second day, [he celebrated] the naval victory at Actium [2nd September, 31 BC]; and
   

4. ✴on the third day, [he celebrated] the subjugation of Egypt [after his victory at Alexandria on 1st August BC]. ...
   

5. All the processions were notable, thanks to the [vast] spoils from Egypt, ... but the Egyptian celebration [itself] surpassed them all in costliness and magnificence. ... [It featured] an effigy of the dead Cleopatra, ... [so that] she, too, together with the other captives and with her children, (Alexander Helios and Cleopatra Selene) was a part of the spectacle and a trophy in the procession”, (‘Roman History’, 51: 21: 5-8).
   

The entries for these triumphs in the fasti Triumphales no longer survive, but those in a manuscript copy of a now-lost fragment of the fasti Triumphales Barberiniani (see Mary Beard, referenced below, p. 304, Figure 37) record the triumphs DE DALMA[T]IS (N°288: 3rd August) and EX A[EGY]PTO (N°290: 5th August): it is possible that the absence from the manuscript of the triumph for the victory at Actium was an error, although, as Mary Beard observed (at pp. 303-4), since Actium:

1. “... had been a victory in a civil war, ... [it] is tempting to imagine that whoever composed or commissioned this particular triumphal list was attempting to ‘clean up’ triumphal history by finessing Actium out of the picture.”
   

Octavianus himself recorded that:

1. “... three time, I have driven triumphal chariots.  In my triumphs, nine kings or children of kings have been led in front of my chariot”, (‘Res Gestae’, 13, translated by Alison Cooley, referenced below, at p. 62).
   

Interestingly, three of these nine unfortunates had been allies of Mark Antony:

1. ✴according to Strabo:
   

2. “... Adiatorix, ... tetrarch of the Galatians. ... a little before the Battle of Actium, ... attacked the Romans by night and slaughtered them ... [After] the victory, ... was led in triumph and [then] executed, together with his son”, (‘Geography’, 12: 3: 6); and
   

3. ✴according to Cassius Dio:
   

4. “...  Alexander [of Emesa] ... , because he had secured his realm [from Mark Antony] as a reward for accusing [Octavian], was paraded in [Octavian’s] triumphal procession and afterwards put to death, (‘Roman History’, 51: 2: 2).
   

Thus, we know that at least five royal personages were paraded in one or other of the last two triumphs (Adiatorix and his son; Alexander of Emesa; and Cleopatra’s children, Alexander Helios and Cleopatra Selene), and it is possible that some or all of the other four were paraded in the first triumph.  As Robert Gurval (referenced below, at p. 33) observed, Octavianus arguably:

1. “... orchestrated [his triple triumph] to exaggerate the magnitude of his foreign conquests and perhaps, at the same time, to make the boast of universal peace.”
   

As he  pointed out, this claim would have been prefigured by the closing of the Janus earlier in the year.

Second Augustan Closure

Cassius Dio referred to a second closure of the Janus in 25 BC, after his victories in Spain:

1. “... Augustus, [as he had become on 16th January 27 BC] closed the precinct of Janus, which had been [re-opened] because of these wars”, (‘Roman History’, 53: 26: 5).
   

The

Augustus had been given the provinciae of Spain, Gaul, Syria and Egypt in the settlement of 27 BC, on the grounds that they all remained insecure, and he duly left Rome in order to campaign in Spain later that year.  As John Rich (referenced below, at p. 156) observed:

1. “... this campaign was the first stage in the promised pacification; ... [it was presumably] marked by the re-opening of the ... Janus and its second closure when he finished campaigning in 25 BC.
   

Third Augustan Closure

As John Rich (referenced below, at p. 162) observed, Cassius Dio referred to a a third senatorial vote to close the Janus in 11 BC:

1. “... on the grounds that the wars had ceased.   However, it was not closed, because
   

2. ✴the Dacians had crossed the frozen Ister and carried off booty from Pannonia; and
   

3. ✴the Dalmatians had rebelled against the [Romans’] exactions of tribute”, (‘Roman History’, 54: 36: 2).
   

He noted that we do not know when it had been re-opened after 25 BC, but:

1. “... it may well have remained closed until Augustus went out to Gaul in 16 BC, immediately following the German invasion of that year.  The third closure is equally mysterious, [since, as Dio recorded, the vote to close it in 11 BC was never implemented and no other closure is recorded in our surviving sources].  It may well be that there [were three senatorial decrees of closure, as Augustus recorded, but] no third closure, and that it remained open from 16 BC until the reign of Nero [see below].”
   

Livy’s Testimony (27 -5 BC)

According to Livy, when Numa succeeded the warlike Romulus, he decided:

1. “... to found Rome anew on [the basis of] justice, laws, and morality.  ... [He realised that, for this plan to succeed, he must first] wean his warlike people from their weapons.  To this end, Ianum ad infimum Argiletum ...  fecit (he built the Janus [shrine] at the bottom of the Argiletum).  In order to signify whether Rome was at peace or at war, it was:
   

2. ✴open when the City was in arms; and
   

3. ✴closed when all Rome’s neighbours had been pacified.
   

4. Since Numa’s reign, [the shrine] has been closed on only two occasions:
   

5. ✴once after the First Punic War, in the consulship, of T. Manlius; and
   

6. ✴again after the battle of Actium [31 BC], ... when imperator Caesar Augustus pace terra marique parta (gave birth to peace on land and sea).
   

7. Numa closed [the shrine] after he had first won over the minds of all the neighbouring peoples with alliances and treaties ... [and thereby secured] relief from foreign dangers ...”, (‘History of Rome’, 1: 19: 1-4; line 1: 9: 3 underlined for reasons discussed below). 
   

Interestingly, Livy refers to Numa’s foundation as ‘the Janus’, which is usually taken to mean a shrine dedicated to Janus.  Livy is the earliest of our surviving sources to attribute its foundation to Numa and to locate it at the bottom of the Argiletum.  (As we shall see, Ovid located it more precisely between two forums, usually taken to mean the spot between Forum Romanum and the Forum Julium, at the start of the road.  No securely-attributed remains of this shrine survive).

In the part of this passage that I have underlined, Liv:

1. ✴followed Varro or his sources by recording the tradition in which the shrine was closed in the consulship of T. Manlius; and
   

2. ✴added its subsequent closure after the battle of Actium.
   

As James Luce (referenced below, at p. 209) pointed out, this passage:

1. “... must [have been written]:
   

2. ✴after 16th January 27 BC, when the title ‘Augustus’ was given to Octavian [= the erstwhile triumvir, imperator Caesar]; and
   

3. ✴before 25 BC, when Augustus closed the [shrine] for a second time, following his subjugation of Spain in the years 27-25 BC [see below].”
   

He also observed that the passage reads more coherently without this underlined passage.  This led him to believe that this underlined passage had been a late addition to Livy’s original text.

As we have seen, Livy associated this closure with the victory at Actium:

1. “... when imperator Caesar Augustus pace terra marique parta (gave birth to peace on land and sea)
   

Carsten Hjort Lange (referenced below, at p. 49) observed:

1. “... [the] first time the slogan ‘pace parta terra marique’ is mentioned in surviving Latin texts is in the inscription of the victory monument at Actium.”
   

Virgil’s Testimony (29-19 BC)

Virgil noted that, in ancient Latium (and later in Rome):

1. “ ... sunt geminae Belli portae (there are twin gates of war)  ... ; they are closed by a hundred brazen bolts and the eternal strength of iron, and Janus, their guardian, never leaves the threshold.  When the Senate is firmly fixed on war, the consul, resplendent Quirinali trabea cinctuque Gabino (in the Quirinal toga, with the toga tucked up in the manner of Gabii, its corner thrown over the left shoulder and brought under the right arm round to the chest), unbars [these] grating portals and ... calls for war.  [This was the way in which, in archaic Latium] Latinus was ordered to proclaim war on the sons of Aeneas ... [When Latinus] shunned the ugly duty, ... [Juno herself], Saturn’s daughter, burst open the iron-bound gates of war”, ‘Aeneid’, 7: 607-23, based on the translations by Henry Rushton Fairclough, referenced below, at pp. 45-7 and Nora Goldschmidt, referenced below, at p. 137).
   

It is possible that, in this passage, Virgil’s gates of war’ came from a line from Ennius’ ‘Annals’ that is preserved by Horace (in a tribute to Ennius’ skill as a poet):

1. “... if you scattered [the words]:
   

2. ‘postquam Discordia taetra Belli ferratos postes portasque refregit (after loathsome Discord broke open the ironbound posts and portals of War’
   

3. ... you would still find the limbs of a dismembered poet”, (‘Satires’, 1: 4: 60-2, translated by Sander Goldberg and Gesine Manuwald, referenced below, at p. 227).
   

As Nora Goldschmidt referenced below, at pp. 137-8) pointed out, while Virgil was describing Juno’s mythical opening of the gates of war in archaic Latium, Ennius’ gates of war would have belonged to the gates of the  Janus at the bottom of the Argiletum in Rome, which had been closed in the consulship of T. Manlius but re-opened in the same year.

Servius (in his commentary on the line ‘sunt geminae Belli portae’) explained that:

1. “Numa Pompilius constructed the sacrarium (place for the keeping of holy things) at the twin gates of war at the bottom of the Argiletum, near the Theatre of Marcellus.  It consisted of two very short templa (shrines), two because Janus was bifrons (two-faced)”, (‘ad Aen.’, 7: 607, based on the translation by Don Fowler, referenced below, at p. 177).
   

Ovid’s Testimony (2-17 AD)

I noted above that Ovid was the source of the key piece of information allowing us to identify more precisely the location of the Janus ‘at the bottom of the Argiletum’.  This came in a passage in the ‘Fasti’, in which Ovid asked Janus:

1. “Why, though there are so many iani (arches) [in Rome], do you stas sacratus (stand consecrated) in only one of them, where you have a templum (sacred place, sanctuary, shrine) joined to two forums?”, (‘Fasti’, 1: 257-8, translated by Steven Green, referenced below, at p. 120).
   

In his commentary on this passage, Green observed (at pp. 120-1) that Ovid implies that this was the only one of the Roman iani in which Janus was officially honoured, and that Ovid’s remark the Janus ‘stands consecrated’ here suggests the presence of  a cult statue.  He also argued (at p. 121) that:

1. “... as Ovid suggests, ... it could be viewed as a [consecrated] corridor joining two forums, the Julium and the Romanum.”
   

Ovid then imagined how Janus explained why he (in the form of his cult statue) stood in this particular arch.  His story was set in the aftermath of Romulus’ infamous abduction of the Sabine women, when the Sabine King Tatius prepared to attack Romulus’ settlement of the Palatine.  He reminded his readers that the traitress Tarpeia (whom he did not actually name) had let into the arx (the citadel on the Capitol), and pointed out that:

1. “From there, as now, there was a steep slope into the valley of the Forum”, (‘Fasti’, 1: 263-4, translated by Steven Green, referenced below, at p. 124).
   

The Sabines stormed down this slope and approached another gate that Juno (see Virgil, above) had opened for them.  Janus then explained how he had come to the Romans’ rescue:

1. “Fearing to engage in battle with so redoubtable a deity [as Juno], I slyly ... opened the mouths of the [nearby] fountains and unleashed a sudden gush of water; but first I threw sulphur into the water channels, so that the boiling liquid might block Tatius’ advance”, (‘Fasti’, 1: 267-72, translated by James Frazer, referenced below, at p. 21).
   

In his account of the same Sabine attack in the ‘Metamorphoses’ (at 14: 785), Ovid had Venus persuade ‘Ausonian nymphs’ to create the gush of sulphurous water at their fountain ‘Iano Iuncta’ (near the Janus)’,  Furthermore, Varro recorded that the name of a fountain known as Lautolae’ derived:

1. “... from lavare (to wash), because there, ad Ianum Geminum (near the Janus Gemini), there were once hot springs:, (‘On the Latin Language’, 1: 157, translated by Roland Kent, referenced below, at p. 147).
   

It is this clear that the speaking statue of Janus in the ‘Fasti’ had blocked Tatius’ advance at Varro’s Porta Ianualis, at the bottom of the Argiletum.  Janus then proudly explained that, in return for his quick thinking:

1. “Ara mihi posita est parvo coniuncta sacello (an altar was set up for me, joined to a little sacellum: the sacrificial spelt and cake are burned in its flames”, (‘Fasti’, 1: 275, translated by James Frazer, referenced below, at p. 21).
   

Steven Green (referenced below, at pp. 127-8) discussed the possible translations of this passage:  Janus might have received:

1. ✴a new altar and a small sacellum in close proximity to each other; or
   

2. ✴a new altar adjoining his existing sacellum.
   

However, if we go back to Ovid’s original question, the choice between these two possibilities becomes clearer.  Ovid asked a ‘speaking’ statue of Janus why, given the existence of so many of the iani in Rome, he ‘stood consecrated’ in the particular arch between the two forums. Clearly, this particular arch existed at the time of Tatius’ attack.  It therefore seems to me that the sacellum was probably a sacred enclosure that had been specifically built to house the statue, and that the nearby altar was added for the sacrifice to him of spelt and cake. 

Nero

Two coins issued at Rome by the Emperor Ner0 (ca. 65 AD) depicting the Temple of Janus ad Infimum Argiletum: 

1. On the left:  Aureus (RIC I² Nero 50):
   

2. Obverse: NERO CAESAR AVGVSTVS, head of Nero;
   

3. Reverse: IANVM CLVSIT: PACE P R TERRA MARIQ PARTA (the doors of the Temple of Janus were closed: Peace of the Roman people on land and sea): short side of the temple)
   

4. On the right:  As (RIC I² Nero 300):
   

5. Obverse: NERO CAESAR AVG GERM IMP, head of Nero;
   

6. Reverse: PACE P R TERRA MARIQ PARTA IANVM CLVSIT S C (Peace of the Roman people on land and sea: the doors of the Temple of Janus were closed by decree of the Senate): two sides of the temple  
   

t

Philip Hill (referenced below, at pp. 10-11) observed, his grandson Nero:

1. “.. celebrated his closure of the shrine by a series of coin-types from Rome and Lyons (Lugdunum), the gold showing the doorway only and the bronze showing the whole shrine [(see the two Roman coins illustrated above). ... According the Suetonius (see below), in 66 AD], the temple of Janus was closed on the occasion of the visit of Tiridates to Rome.”
   

The passage by Suetonius has been translated as follows:

1. “I may fairly include among [Nero’s] shows the entrance of Tiridates into the city.  (He was a king of Armenia, whom Nero induced by great promises to come to Rome) ...  [Nero exhibited] him at the first favourable opportunity, with the Praetorian cohorts drawn up in full armour about the temples in the Forum.  [During the ceremony, Nero] himself sat in a curule chair on the rostra in the attire of a triumphing general, surrounded by military ensigns and standards.  ... From there, [he accompanied] the king... to the theatre [of Pompeius Magnus] ... Because of all this, Nero was hailed as Imperator and, after taking his laurel wreath in the Capitol, Ianum geminum clausit (he closed the temple of Janus Geminus/ Janus bifrons or two-faced), as a sign that no war was remaining”, (‘Life of Nero’, 13).
   

Temple Location

Plan of the Imperial Fora, including the stretch of the Argiletum between the Forum Romanum and the Forum Julium

Adapted from the image in this page of the website Caveat Lector: Reading Ancient Rome (my additions in red)

I discuss the closing of the ‘gates of war’ further below.  For the moment, we should simply note that the ‘temple’ attributed to Numa was actually a small shrine made up of two gated arches that were connected by two longer side-walls.  As we have seen, a number of our surviving sources cited at the bottom of the Argiletum.  Ovid fortunately gave further information: during an imagined interview with Janus, Ovid enquired:

1. “When there are so many iani,(arches [in Rome],why do you, [Janus], stand consecrated in the one here, where you have a templum joined to two fora”, (‘Fasti’, 1:  257-8, basted on the translation by Rabun Taylor, referenced below, at p. 26-7). 
   

2. Since Ovid was writing about a century before before the building of the Forum of Nerva, it is usually assumed that the shrine was on the edge of the Forum Romanum and close to adjoining the Forum Julium (completed in 46 BC).  No archeological remains of this shrine have ever been securely identified, although it apparently survived into the 6th century AD, when the Byzantine historian Procopius recorded that Janus:
   

3. “... has his temple in ... the [Roman] forum, in front of the [Curia Julia, which had been rebuilt by the Emperor Domitian and heavily restored after a fire in 285 AD. ... The temple] is entirely of bronze and was erected in the form of a square, but it is only large enough to cover the statue of Janus.  Now this statue, which is of bronze, is not less than 5 cubits [about 7.5 ft] high; it resembles a man in all other respects, except that its head has two faces, one of which is turned toward the east and the other toward the west.  And there are brazen doors fronting each face.  In pagan times, the Romans used to close [these doors] in times of peace and prosperity but open them in times of war.  When they came to honour ... the teachings of the Christians, they abandoned the custom of opening these doors, even when they were at war.  However, [when Vittigis, king of Ostrogothic Italy, laid siege to Rome in 537-8 AD, when Procopius was in the City], some of them who presumably remembered the old belief secretly tried to open the gates, but they [hardly managed to move them]”, (‘History of the Wars’, 5: 25: 18).
   

It is likely that Procopius was describing a temple that had replaced that of Numa at the time of Domitian’s rebuilding of the Curia Julia.

Cult Statue of Janus Geminus

According to Pliny the Elder:

1. “Various circumstances prove that the art of making statues was commonly practised in Italy from an early period: 
   

2. ✴Evander is said to have dedicated the statue of Hercules in the Forum Boarium; it is called Hercules Triumphalis and, on the occasion of triumphal processions, is arrayed in triumphal vestments.
   

3. ✴And then, King Numa dedicated the statue of Janus Geminus, a deity who is worshipped as presiding over both peace and war.  The fingers [of this statue] are so formed as to indicate the 365 days of the year, thus denoting that [Janus] is the god of time and eternity”, (‘Natural History’, 34: 16).
   

It is usually assumed that the second of these statues was the cult statue of Janus in his temple at the bottom of the Argiletum: as we have seen, Procopius described the cult statue here in the 6th century AD as an oversized bronze figure of the two-faced Janus, which looked simultaneously towards the eastern and the western gates of the shrine. 

However, as is often pointed out

Gates of War

Livy recorded that the gates of the temple of Janus

1. “...  have been closed twice since the reign of Numa:
   

2. ✴for the first time, during the consulship of T. Manlius [in 241 BC], after the First Punic War; and
   

3. ✴for the second time (which the gods granted our generation to see) after the war at Actium [in 31 BC], when the commanding general, Caesar Augustus, achieved peace on land and sea”, (‘History of Rome’, 1: 19: 3).
   

Pliny the Elder

1. “Silver was not impressed with a mark until the year... the consulship of Q. Ogulnius and C. Fabius [269 BC], five years before the [start of the] First Punic War; at which time it was ordained that the value of the denarius should be ten libræ of copper, that of the quinarius five libræ, and that of the sestertius two libræ and a half.  However, the weight of the libra of copper was diminished during the First Punic War, when the Republic lacked the means to meet its expenditure: in consequence of which, an ordinance was made that the as should in future be struck of two ounces weight.  By this contrivance, a saving of five-sixths was effected, and the public debt was liquidated.  The impression upon these copper coins was a two-faced Janus on one side, and the beak of a ship of war on the other”, (‘Natural History’, 33: 13).
   

Servius (in his commentary on the line ‘sunt geminae Belli portae’) explaied that:

1. “Numa Pompilius constructed the sacrarium (place for the keeping of holy things) at the twin gates of war at the bottom of the Argiletum, near the Theatre of Marcellus.  It consisted of two very short templa (shrines), two because Janus was bifrons (two-faced) ...
   

2. ✴[Some authors consider] him to be the lord of the days, in which there is the sunrise and then the sunset (as in Horace, [who refereed, at ‘Satires’, 2: 6: 20 to the] father of dawn, or Janus, if you prefer).
   

3. ✴Others [consider him to be quadrifons and the lord of] the whole year, which ... is divided into four seasons.  (That Janus is the lord of the year is ... [evidenced by the fact that its opening month], January, is named for him)”, (‘ad Aen.’, 7: 607, based on the translation by Don Fowler, referenced below, at p. 177).
   

Servius also commented directly on the cult of Janus to which Virgil had referred:

1. “Some call him ... Mars, and [say] that, because he has the greatest  power among the Romans, he is honoured first [among the god] in cult.  Others say that he is air and thus the father of speech, which is why he is entrusted with taking our prayers to the [other gods]gods. ... He is sometimes called:
   

2. ✴[Janus] Junonius, [which makes it fitting that Virgil brings] Juno in to open the gates [of war]; or
   

3. ✴[Janus] Quirinus, [which is why, as Virgil noted], they say that the consul opens the gates [of war Quirinali trabea] ... ”, (‘ad Aen.’, 7: 610, based on the translation by Don Fowler, referenced below, at pp. 177-8).