Fontana dei Dioscuri

The Fontana dei Dioscuri is the fountain set opposite the Palazzo del Quirinale, the official residence of the President of the Italian Republic in the Piazza del Quirinale.

The original fountain, which no longer exists, commissioned by Pope Sixtus V in 1588, had the Dioscuri, Castor and Pollux statues, from Constantine I of Rome's Baths, moved to the piazza, from the site, thought to have been nearby, flanking it.

In the late 1780s by Antinori, was commissioned by Pope Pius VI, to make a better layout for the piazza and had the fountain and the Dioscuri moved, and included the large Obelisk which had been moved from the Campus Martius in the design.

Source: Wikipedia