It is a large square, trapezoidal in shape, closed to the northern side by the city walls and connected to the city via Porta Valbona. While the eastern side borders the whole Ducal Stables building (la Data), moreover in the north-eastern corner there is the rampart ramp, which has an entrance right on this square. The western side is occupied by the houses of Borgo Mercatale and immediately behind it rises the hill of Vigne. Behind the retaining wall of the square, there is a small garden once occupied by the church of San Rocco and the Oratory of Sant'Antonio Abate, demolished in the 1920s.

The square was built thanks to the waste earth, obtained during the excavations for the construction of Palazzo Ducale, and to ensure greater stability in the buildings of the Ducal Stables, the helical ramp and the Palazzo Ducale itself.

Until the first half of the twentieth century, the square was the site of commercial activities (from which it took its name). But not only that, because in the 16th century games were held with animals (Corrida del Mercatale), jousting and knightly tournaments. From July 15, 1875, the square hosted the matches of "Palla col bracciale", with the field leaning against the wall of the Ducal Stables, for a length of over one hundred meters. Also in the 19th century, until the first half of the following century, a cattle fair, was held on public holidays.

The function of Mercatale changed in the second half of the twentieth century, following the intervention of architect De Carlo; with "Operazione Mercatale" (1969-1972) he designed the construction of an underground two-storey car park in the square; followed by the arrangement of an above-ground parking lot.