Siena is the embodiment of a medieval city. Its inhabitants pursued their rivalry with Florence right into the area of urban planning. Throughout the centuries, they preserved their city's Gothic appearance, acquired between the 12th and 15th centuries. During this period the work of Duccio, the Lorenzetti brothers and Simone Martini was to influence the course of Italian and, more broadly, European art.
The whole city of Siena, built around the Piazza del Campo, was devised as a work of art that blends into the surrounding landscape.
Siena, an outstanding medieval city that has preserved its character and quality to a remarkable degree, and its influence on art, architecture and town planning in the Middle Ages, both in Italy and elsewhere in Europe, was great.
The historic centre of Siena is delimited by a 7km enceinte of ramparts (14th-16th centuries), the route of which follows the contours of the three hills on which the city is built. These walls, with their bastions and towers, are pierced by gates that are double at the strategic points, such as the Porta Camollia on the street of Florence. To the west they embrace the Fort of Santa Barbara, rebuilt by the Medici in 1560 and reconstructed in 1580. The walls themselves, which have been enlarged on several occasions, also include part of the 25 km network of galleries, the bottini, which evacuate the spring waters distributed by the public fountains. Siena doubtless benefited from the experience of the monks of the Cistercian abbey of San Galgano. The main fountains, mostly from the 13th century, are veritable buildings in their own right, constructed like Gothic porticoes.
The historic centre developed along the Y-shaped segments defined by the three main arteries that meet at the Croce del Travaglio, represented by the Piazza del Campo, and on to which the network of minor roads are grafted. Houses and palaces follow one another in rows along the main streets, creating a characteristic urban space with certain notable elements. The Piazza del Campo, sited at the junction of three hills, is one of the most remarkable urban open spaces in all Italy. Its formation coincides with the growth of the medieval city and the assertion of communal power. Financial and commercial activities were concentrated halfway along the Via Francigena, the entire lengths of the present-day Via dei Banchi Sopra and Via dei Banchi Sotto, and the market-place proper was located in the Piazza del Campo, at that time divided in two sectors.
At the end of the 12th century, the communal government decided to unite the two sectors to create a unique semicircular open space, and promulgated a series of ordinances which regulated only commercial activities but also the services and dimensions of the houses (their style twin-arched or triple-arched windows), in order to make the facades around the piazza uniform. The building of the Palazzo Pubblico, the seat of the communal government, began at the same time. Its gently incurving and crenellated facade is highlighted by the Gothic triple-arched windows. There is a number of masterpieces of medieval paintings inside, such as the Maestà of Simone Martini and the allegorical Ciclo del Buon Governo of Ambrogio Lorenzetti. The Palazzo Pubblico was in all probability the model for the Gothic palaces of the great families of the nobility or the merchants (Palazzo Tomei, Palazzo Buonsignore), which are characterized by an increase in breadth, the use of brick, large windows, and the so-called 'Guelph' crenellation.
Once the public authorities were installed in the Palazzo Pubblico, work began on embellishing the piazza with the laying down of the paving, construction of the Fonte Gaia, decorated by Jacopo dalla Quercia, the Torre del Mangia, and the Cappella della Piazza, the latter two built up against the palazzo. Under the Medici, the piazza became the ideal setting for spectacular festivals and was opened up to the palio , the famous horserace between teams from the different quarters of the city.
The highest point of the town is crowned by the Cathedral of Santa Maria. Its facade, the lower part of which is the work of Giovanni Pisano, was completed by Giovanni di Cecco after construction of the Nuovo Duomo (New Cathedral), a vast project inspired by the Gothic cathedrals of north of the Alps. The cathedral preserves a remarkable pavement and the pulpit carved by Nicolà Pisano.