Set into the back of the Palazzo Poli, the fountain is at the juncture of three roads (tre vie). It marks the terminal point of the "modern" Acqua Vergine, the revitalised Aqua Virgo, one of the aqueducts that supplied water to ancient Rome. 

Designed by Nicola Salvi, the fountain was completed in 1762, when Pietro Bracci's 'Neptune' was set in the central niche. The fountain was refurbished in 1998. The custom is to throw three coins over your shoulder at the same time: the first coin for true love, the second for a good marriage and the third is for you to return to Rome.