The Temple of Castor and Pollux (Italian: Tempio dei Dioscuri) is an ancient temple in the Roman Forum, Rome, Central Italy. It was originally built in gratitude for victory at the Battle of Lake Regillus (495 BC). Castor and Pollux (Greek Polydeuces) were the Dioscuri, the "twins" of Gemini, the twin sons of Zeus (Jupiter) and Leda. Their cult came to Rome from Greece via Magna Graecia and the Greek culture of Southern Italy.
The Roman temple is one of a number of known Dioscuri temples remaining from antiquity.
During the Republican period, the temple served as a meeting place for the Roman Senate, and from the middle of the 2nd century BC the front of the podium served as a speaker's platform. During the imperial period, the temple housed the office for weights and measures, and was a depository for the State treasury. Chambers located between the foundation piers of the temple were used to conduct this business. Based on finds from the drains, one of the chambers was likely used by a dentist.
The archaic temple was completely reconstructed and enlarged in 117 BC by Lucius Caecilius Metellus Dalmaticus after his victory over the Dalmatians. Gaius Verres again restored this second temple in 73 BC.
Commemorating the initial victory at Lake Regillus, a large cavalry parade was held each year on July 15 and featured as many as 5,000 young men carrying shields and spears. Two young men, riding white horses, led the parade and represented Castor and Pollux.
In 14 BC a fire that ravaged major parts of the forum destroyed the temple, and Tiberius, the son of Livia by a previous marriage and adopted son of Augustus and the eventual heir to the throne, rebuilt it. Tiberius' temple was dedicated in 6 AD. The remains visible today are from the temple of Tiberius, except the podium, which is from the time of Metellus.
In conjunction with this imperial rebuilding, the cult itself became associated with the imperial family. Initially, the twins were identified with Augustus's intended heirs, Gaius and Lucius Caesar. After their premature deaths, however, the association with Castor and Pollux passed to Tiberius and his brother Drusus.
According to Edward Gibbon, the temple of Castor served as a secret meeting place for the Roman Senate. Frequent meetings of the Senate are also reported by Cicero. Gibbon said the senate was roused to rebellion against Emperor Maximinus Thrax and in favor of emperor Gordian I and his son Gordian II at the Temple of Castor in 237 AD.
If still in use by the 4th-century, the temple would have been closed during the persecution of pagans in the late Roman Empire. The temple was possibly already falling apart in the fourth century, when a wall in front of the Lacus Juturnae was erected from reused material. Nothing is known of its subsequent history, except that in the 15th century, only three columns of its original structure were still standing. The street running by the building was called via Trium Columnarum.
In 1760, the Conservatori, finding the columns in a state of imminent collapse, erected scaffolding for effecting repairs. Both Piranesi and the young English architect George Dance the Younger were able to climb up and make accurate measurements; Dance had "a Model cast from the finest Example of the Corinthian order perhaps in the whole World", as he reported to his father.
Today the podium survives without the facing, as do the three columns and a piece of the entablature, one of the most famous features in the Forum.