The battle ended quickly, and about the same time, two knights on gleaming white horses rode into the Forum Romanum -- a highly unusual event, because armed men were not allowed into the sacred city boundary, the Pomerium, and certainly not into the Forum. These two silently dismounted and led their steeds to drink at the pool of Juturna, right beside the temple of Vesta. A crowd gathered and eventually someone had the courage to ask the knights what they were about. Their only response was that the Roman army had just defeated the final attempt to restore the monarchy. In the wild celebration that followed, everyone lost track of the two, and they were not seen again.
It was only when the Roman army returned to the city and told the story of the battle that the priests realized that Rome had been saved by intervention of the gods, and it took some research to determine who they were: the Dioskouroi were known to the Etruscans and worshipped by the Greeks, but they were hardly known at all in Rome. But soon everyone knew about the Dioskouroi, and a magnificent temple was erected to the twins, the first foreign temple allowed inside the Pomerium. Three huge pillars from that temple, 45 feet tall and surmounted by a thirteen foot tall section of the architrave, still stand on the site just west of the remains of Vesta's temple. Another great temple to Castor and Pollux was later erected near Tiber River at the southern end of the Campus Martius, and in front of that temple, paid for and dedicated by the Roman Equites (the knightly class), stood magnificent statues of Castor and Pollux and their horses. Like other Roman statues, Castor and Pollux were painted in naturalistic colors, but the horses were left unpainted, and the white marble gleamed in the sunlight.
The Flaminian Field, later called the Circus Flaminius, was near the riverside temple. Horse races of the non-religious games were started there, and there, also, the horses were hitched to the chariots of victorious generals before their grand parades into the City. And every year on the Ides of July, the Roman equites, after first meeting at the pool of Juturna in the Forum, rode forth from the Circus Flaminia and through the Caffarella Valley toward Frascati to commemorate the god-aided victory.
Another set of statues of men with horses, often identified as Castor and Pollux, stand in the Piazza del Quirinale in front of the Presidential Palace. Unlike most ancient Roman statues, the Quirinale horsemen have been visible and in the same general area since they were copied from an ancient Greek bronze and set up in front of the Baths of Constantine, which stood nearby. They were misidentified as works of the Greek sculptors Phidias and Praxitiles at the end of the 16th century. The statues were finally moved to their present position at the end of the 19th century when they were grouped with the obelisk that had been moved from the Augusteum. Because of the presence of the statues, the Quirinale has long held the sobriquet "Monte Cavallo."
Already in ancient Roman times Castor and Pollux became conflated in popular legend with Romulus and Remus. And when two sons of Augustus died in their teens or early twenties, long before the death of Augustus himself, they were also eulogized as reincarnations of Castor and Pollux, but that probably reflected ingratiation by the eulogists rather than popular belief.
A millennium and a half later when Michelangelo was looking for a decorative theme for the redesign of the Campidoglio, he chose the Dioskouroi. The fragmented statues of Castor and Pollux and their mounts had been discovered in 1561 at the site of their riverside temple. Michelangelo repaired and re-erected them on opposite sides of the Cordonata, the ramp leading up to the Piazza del Campidoglio. In the center of the Piazza he emplaced the bronze equestrian statue of Marcus Aurelius, which he moved from the front of the Lateran palace, and chose for its carved base a massive block of white marble from the Castor and Pollux Temple in the forum.
The Battle of Lake Regillus,
from the Lays of Ancient Rome, by Thomas Babbington
Bullfinch -- The Dioskouroi myth
The Forum Temple (with a picture):
Images of the Campidoglio:
Images of Castor and Pollux, the
Images of the Forum Temple: