The Tempio dei Dioscuri (the Temple of Castor and Pollux) was dedicated on 15 July 484 BCE (the Ides of July) as thanks for the Roman victory at the Battle of Lake Regillus (495 BCE) where Castor and Pollux, associated with cavalry, were said to have appeared at the head of the Roman. The remaining structure is from the later reconstruction completed by Emperor Tiberius in 6 CE. The temple frequently served as a meeting place for the Roman Senate, and the standards of weights and measures were also stored there.
“Temple of Castor and Pollux” http://penelope.uchicago.edu/~grout/encyclopaedia_romana/romanforum/castor.html
“Temple of Castor and Pollux” Ancient History Encyclopedia http://www.ancient.eu/article/632/
Temple of Castor and Pollux, Rome
The Roman Forum
Bust of Tiberius, Romisch-Germanisches Museum, Cologne