The Temple of Castor and Pollux (Italian: Tempio dei Dioscuri) is an ancient temple in the Roman Forum. It was originally built in gratitude for victory at the Battle of Lake Regillus (495 BC). Castor and Pollux were the "twins" of Gemini, the twin sons of Zeus (Jupiter) and Leda.
In 1760, the columns were in a state of imminent collapse so the "conservatori" had them repaired.
Obviously, the rest of the temple is long gone.