Forum Romanum | Temple of Castor and Pollux (three columns on the left, 6AD) 
Castor and Pollux are twins in a mythological story and also patrons of the equestrians. The Roman dictator Postumius promised to build a temple for the twins if he would win a certain battle. According to a myth, both appeared on the battle field to help the Romans to the victory. Afterwards, the twins appeared on the Forum to announce the victory.