Public square in the ancient zone of the Boarium Forum, in front of the Tiber' island, which takes its name from the Boccà della Verità, today located in the porch of the church of Santa Maria in Cosmedin.

Besides the going back church to the late Middle Ages, in the public square they rise the Arch of the Argentari, Arch of Giano, the Temple of Hercules, erroneously identified as Temple of Vesta in reason of its circular form, and the Tempio di Portuno, divinity tied to the fluvial port that rose here.

The fountain in front of the two temple, realized by Carl Bizzachieri on a commission basis of Pope Clemente XI, was placed in the public square in 1715, it has an octagonal base and represents two tritons that support a shell over the witness from which she gushes out the water.

Here till the 1868 came executed the condemned ones.