The square is located in the focal point where the three main branches off the streets, spines of others, standing out as one unit of sublime harmony, highest fruit of the passion for the beauty of Siena, manifested early by the people even before the famous statute in 1262 dedicated to urban planning and aesthetics town. This makes it one of the highest creations of medieval.
The shape of the square is emiciclica, resembling a valve of a shell inclined toward the south, with nine segments defined by white bands on the brick floor. Enclosed by the almost continuous curtain of buildings, it will branch out eleven gates (formerly twelve), cleverly masked by the use of the time and the arrangement of multiple layers of the settlement. The geometry appears cleverly combined with the shape of the territory, coming to translate the peculiarities of the place in an environment designed. The centerpiece of the whole square is the Public Palace, which closes the space spectacularly downstream and towards which all lines of sight, the differences in height, the building facades and flooring, emphasizing the symbolic value.
The circumference is 333 square meters and is divided into two areas: “low”, invaded the central and south, paved with bricks arranged a “knife” and divided into nine segments, and the curtain around, paved. Number nine would evoke the Government of the Nine.