Now, in this passage, we think we have an explanation of why it is called the Stairs of Caius, not Cacus. This name does not refer to Cacus, the shepherd robber, who had his cave on the Aventine, but, as we learn from the above passage from Plutarch, to Caius the emperor, who was nicknamed Caligula from his having worn the sandals so-called of the Roman troops—he having been brought up in the camp on the banks of the Rhine, Caius being his proper name. He, as we have seen, repaired these steps, and so they were called after him; but that was not their previous name. The question arises, What was that name? Why, none other than the Porta Carmenta, the missing third gate of Roma Quadrata, "the gate since called Carmental by the Roman state."
It was up this gateway that the Romans brought the Sabine women when they ran off with them in the Circus Maximus. Valerius Antias says they were five hundred and forty-seven in number; Plutarch says there were six hundred and eighty-three, and that the event took place on the 18th of August.
But before this the gate had another name, the original name in the Arcadian period. We know from Virgil and Diodorus Siculus that it existed before the time of Romulus, and was incorporated by him into his city. Let us see what that name was.
"Hercules, after he had gone through Liguria and Tuscany, encamped on the banks of the Tiber, where Rome now stands, built many ages after by Romulus, the son of Mars. The natural inhabitants at that time inhabited a little town upon a hill, now called Mount Palatine. Here Potitius and Pinarius, the most eminent persons of quality among them, entertained Hercules. There are now at Rome ancient monuments of these men; for the most noble family, called the Pinarii, remains still among the Romans, and is accounted the most ancient at this day. And there are Potitius's stone stairs to go down from Mount Palatine (called after his name), adjoining to that which was anciently his house" (Diodorus Siculus, iv. 1). Thus we see that the spot was originally called the Stairs of Potitius.
Virgil ("Æn.," viii.) informs us that Potitius, the Arcadian high priest, instituted the worship of Hercules; and that the priests were selected from the Pinarian house.
"When the new walls were built by Servius Tullius, one of his gates was named Carmentalis after the above tradition; the original Porta Carmenta having become obsolete."
The valley between the Palatine and Aventine, the site of the Circus Maximus, was formerly the Murzian Lake or bay, formed by an arm of the Tiber, and these stairs led down to the fair shore (Pulcrum Littus, Καλὴ Ἀκτή )—that is, to the shore of the lake, where Æneas landed—and this had nothing to do with the banks of the Tiber, which would hardly be called a fair shore by Plutarch. Virgil calls it "the strand."
The above name was also given to one of the temples.
THE TEMPLE OF ROMA QUADRATA (6).
"A certain hallowed place on the Palatine before the Altar of Apollo Rhamnusii (5), which every city built with Etruscan rites contained, and in which were placed those things considered of good omen in founding a city" (Festus). This hallowed place, as well as the city, was called by Romulus Roma Quadrata.