The fountain consists of an ancient porphyry trough which was taken from the Roman baths. On top of the water fountain is a large marble tablet with a kind of scroll on each side, both scrolls are topped with balls made of travertine stone. The center of the tablet is occupied by an enormous mask in white marble, a mask which could be dated back to the Ancient Romans. Water spurts from the figure’s half-open mouth. The figure is kind of odd-looking with hair parted in the middle and falling below the chin to frame the face and with a fixed, empty look in its eyes. At the very top of the tablet there is a huge fleur de lys, a sure sign that the "Big Mask" was erected under the auspices and at the expense of the Farnese family in 1626.

The Via Giulia we see today is quiet and rather forgotten rather the opposite when Julius II had it opened up at the beginning of the 16th century. During that time, it was the main street and the most elegant road in the city, remaining that way for many years. It was used for many festivals and ceremonies. However in 1720, on the third day of Pentecost, all the Roman nobles wanted to take the air in Via Giulia to show off their most precious finery and their most expensively furnished carriages in honor of the election of a new Grand Master of Malta. A copious stream of delicious wine began to flow from the Big Farnese Mask fountain which did not stop till four in the morning. It was the wish of the authorities to extend the day's rejoicing into the evening, with a pleasing display of fireworks and, before that, to illuminate the street with huge round flat tallow candles.