Piazza del Campo, the heart of the civil life of Siena, with its superb and monumental architecture, is one of Italy's most fascinating public spaces. Built in the communal period, when it was used as a marketplace - as twelfth-century documents testify, referring to it as the Campus Fori - the lovely square, with its characteristic shell shape, was laid out in its present form towards the end of the thirteenth and the first half of the fourteenth century. That was when it was paved with red brick and subdivided by long strips of light stone into nine sectors, in memory of the government of the Nine and provided with the most important buildings in the city. The vast square is bounded by elegant fourteenth-century crenellated and turreted palazzos, gently dropping down from either side towards the massive bulk of the Palazzo Pubblico, a brilliant example of Gothic architecture, erected at the end of the thirteenth century as the residence of the Signoria and of the Podestà, and nowadays both the City Hall and the interesting Civic Museum. This building has a fine harmonious front, arched at ground floor level, while above, there are two orders of three-light windows and the top floor with two-light windows and adorned with cornices and crenellation and at the centre a fifteenth-century copper plaque, bearing a monogram of Christ. Enlarged with the addition of two side wings, the palazzo was completed in the first half of the fourteenth century with the slender brick Mangia tower, built by Muccio and Francesco di Rinaldo. 88 m. high, the tower was finished off with splendid coping in white travertine and given an elaborate belfry, the work of Agostino di Giovanni. During the Middle Ages, the Palazzo symbolised the political and economic autonomy of Siena. At the foot of the tower the marble Cappella di Piazza stands out, erected in the fourteenth century by Giovanni di Cecco in the course of the terrible plague that hit the city. Also standing facing the square are the majestic Palazzo Sansedoni, with its curvilinear façade, spaced by elegant three-light windows and surmounted by a slender tower, despite considerable rebuilding, it has preserved its medieval appearance, and the elegant Rinnovati theatre, once the Chamber of the Great Council of the Republic. Finally, the upper part of the square contains the Gaia Fountain, a splendid nineteenth-century reproduction, carried out by Tito Sarrocchi, of the original square-shaped fountain, built between 1409 and 1419, by Jacopo della Quercia and at one time adorned by enchanting marble sculptures, nowadays to be seen in the loggia of the Palazzo Pubblico. Every summer, of course, the superb Piazza del Campo is the setting for the world-famous Palio, the spectacular, thrilling horse race of medieval origins, which involves the city's ten Contrade, or quarters, attracting a huge crowd of onlookers.