The unusual shell shape makes Piazza del Campo in Siena a unique place throughout the world, and it is considered one of the most beautiful squares in Italy. The people of Siena know it as 'il Campo' and it has always been the centre of city life. It slopes slightly towards the Palazzo Pubblico, the town hall, which is overshadowed by the Torre del Mangia. The Palio, held here twice a year, is the most important historical-folkloristic event in Italy. This is a horse race in which ten of the seventeen districts of Siena compete in turn, attracting numerous Italian and foreign tourists.