The Temple of Castor and Pollux, also known as the Temple of the Dioscuri, was first built in 484 BCE. However, what we see today are the remains of the building inaugurated by Tiberius in 6 CE, during the reign of the emperor Augustus.
The temple had eight Corinthian columns at the front and back and eleven along the long sides. There was a single cella paved with mosaics. The podium measures 32 m by 49.5 m and is 7 m high. During the Imperial period, it housed the office for weights and measures.
The cult of Castor and Pollux (also known as the Dioscuri), twin brothers and demi-gods, was adopted in Rome in 496 BCE after the Battle of Lake Regillus, where they are said to have led the cavalry charge that led to the victory of the Romans over the Etruscans. During the fighting they miraculously appeared in the Forum, calmly watering their horses by the Temple of Vesta. This was taken as a sign that the Romans had been victorious.
Rome's equestrian class regarded Castor and Pollux as its patrons and each year, on July 15th, they held a grand parade in front of the temple. As many as 5,000 young men took part, carrying spears and shields, wearing olive wreaths and purple robes decorated with scarlet bands, and led by two youths on white horses, representing the Dioscuri.
For centuries the surviving trio of Corinthian columns (12.5 m high), which are known locally as 'le tre sorelle' (the three sisters), have been one of the most prominent landmarks of the Forum Romanum.