The walled city of Siena is made up of three areas or terzi (Terzo di Camollia, Terzo di Citta, Terzo di San Martino), each of which is subdivided into a number of contrade (wards/districts). There are seventeen contrade in all and it is to the contrada, membership of which is strictly by birth, that a citizen of Siena owes his or her first allegiance.
Each contrada, most of which are named after animals (oca/goose, istrice/porcupine,civetta/owl), has its own flag and colours, its own chapel, museum and fountain, and, of course, its own patron saint. Each contrada also has its traditional allies and adversaries. Only the Nobile Contrada della Oca and the Contrada della Lupa have no allies; while four, Bruco, Drago, Giraffa and Selva, have no declared adversaries.
Twice a year, on July 2nd and August 16th, the contrade compete in the Palio di Siena, the now world famous horse race, which takes place in the neutral space of the Piazza del Campo.