This sloping piazza, popularly known as Il Campo, has been Siena's civic and social centre since being staked out by the Consiglio dei Nove in the mid-12th century. It was built on the site of a former Roman marketplace, and its pie-piece paving design is divided into nine sectors to represent the number of members of the council. In 1346 water first bubbled forth from the Fonte Gaia (Happy Fountain) in the upper part of the square. These days, the fountain's panels are reproductions; the severely weathered originals, sculpted by Jacopo della Quercia in the early 15th century, are on display in the Complesso Museale Santa Maria della Scala.

At the lowest point of the square stands the spare, elegant Palazzo Comunale, conceived by the Consiglio dei Nove as a nerve centre for the republican government, uniting the offices and courts in one building and thus greatly reducing the symbolic and actual power of the feudal nobles.

Dating from 1297, the palazzo (palace) is one of the most graceful Gothic buildings in Italy, with an ingeniously designed concave facade that mirrors the opposing convex curve formed by the piazza. Also known as the Palazzo Pubblico, or town hall, it was purpose-built as the piazza's centrepiece, resulting in a wonderful amphitheatre effect. It now houses the Museo Civico.

Entry to the ground-floor central courtyard is free. From it soars the graceful Torre del Mangia, 102m high and with 500-odd steps. The views from the top are magnificent, but if you want to see them you should expect to wait in high season, as only 30 people are allowed up at any time.

The Campo is the undoubted heart of the city. Its magnificent pavement acts as a carpet on which students and tourists picnic and relax, and the cafes around the perimeter are the most popular aperitivo (pre-dinner drinks) spots in town.