a traditional medieval horse race run around the Piazza del Campo twice each year, on 2 July and 16 August. The event is attended by large crowds, and is widely televised. Ten randomly selected from 17 Contrade (which are city neighbourhoods originally formed as battalions for the city's defence) vie for the trophy: a painted banner, or Palio bearing an image of the Blessed Virgin Mary. Art Over the centuries, Siena has had a rich tradition of arts and artists. The list of artists from the Sienese School include Duccio and his student Simone Martini, Pietro Lorenzetti and Martino di Bartolomeo. A number of well-known works of Renaissance and High Renaissance art still remain in galleries or churches in Siena. The Church of San Domenico contains art by Guido da Siena, dating to the mid-13th century. Duccio's Maestà, which was commissioned by the City of Siena in 1308, was instrumental in leading Italian painting away from the hieratic representations of Byzantine art and directing it towards more direct presentations of reality. And his Madonna and Child with Saints polyptych, painted between 1311 and 1318, remains at the city's Pinacoteca Nazionale. The Pinacoteca also includes several works by Domenico Beccafumi, as well as art by Lorenzo Lotto, Domenico di Bartolo and Fra Bartolomeo. Main sights The Siena Cathedral (Duomo), begun in the 12th century, is a masterpiece of Italian Romanesque–Gothic architecture. Its main façade was completed in 1380 with a nave oriented northeast–southwest. A proposed expansion of the eastern transept would have transformed the church into an ambitiously massive basilica, the largest then in the world, with an east–west nave. However, the scarcity of funds, in part due to war and the Black Death, truncated the project. Two walls of this expanded eastern transept remain; through an internal staircase, visitors can climb for a grand view of the city. The Siena Cathedral Pulpit is an octagonal 13th-century masterpiece sculpted by Nicola Pisano with lion pedestals and biblical bas-relief panels. The inlaid marble mosaic floor of the cathedral, designed and laboured on by many artists, is among the most elaborate in Italy. The Sacristy and Piccolomini library have well-preserved Renaissance frescos by Ghirlandaio and Pinturicchio respectively. Other sculptors active in the church and in the subterranean baptistry are Donatello, Lorenzo Ghiberti, Jacopo della Quercia and others. The Museo dell'Opera del Duomo contains Duccio's famous Maestà (1308–11) and various other works by Sienese