The Temple of Castor and Pollux is readily recognizable by its remaining 3 white columns standing in a line close by the Temple of Vesta.  These columns are part of the side of a much later rebuild of what was originally a 5 Century BCE temple. The original temple to the semi-divine twins Castor and Pollux was pledged just after 500 BCE by Aulus Postumius Tubertus - an early Roman military leader. 

According to legend, Jupiter’s mortal son Castor and his immortal son Pollux came riding into battle in aid of Rome’s forces – the twins were seen by Postumius and his immediate troops. The semi-gods were carrying spears, riding white horses and helped guide an attack of the Roman troops. They were then seen again, later that same day, at the spring of Joturna where they spread news of Rome’s victory.  The Temple and Spring of Joturna are very close by.

In the early second century BCE the temple was repaired by possibly Aemilius Paullus in celebration of his victory over the Macedonians. Further modifications and updates were made by Lucius Caecilius Metellus and then by the Emperor Augustus following the devastating fire of 14 or 9 BCE.  He used the repairs to better associate the temple and the divine twins with his own two sons - Gaius and Lucius Caesar. Sadly, both children would die before completion of the project and so, in time, the association changed to be with Tiberius and his late brother Drusus.

In the course of all these repairs and updates the design was changed to be of a form similar to other adjacent forum temples such as that of Divus Julius.  The updated version had two sets of steps flanking the entrance, a row of 8 columns at the front and back and 11 columns on each side.  The 3 remaining columns, which have Corinthian capitals, are from the middle section of the east side.  They support a simple but elegant entablature that would have run around the entirety of the edge of the roof – most likely with a carved dedication on the front that faced North. Ascending the steps at the front one would have passed through the front columns, under a large triangular pediment and into a single main temple hall that likely contained statues of Castor and Pollux.

Given that the temple has a raised podium fronting directly onto the Forum it also served as an orators platform. Perhaps surprisingly, the extremely solid base of the temple’s foundations was divided into chambers for various official public services - particularly those needing the protection of thick walls. 

In addition to its civic function, the Temple was the center of annual celebrations commemorating the victory at Lake Regillus.  A major cavalry parade was held each year on July 15th and featured as many as 5,000 young men carrying shields and spears.