It is a formally choreographed triumphal march that commemorates the ancient institutions, customs and greatness of the Republic of Siena.
In the early afternoon, on the day of the Palio, members of the town gather in the courtyard of the Palace of Justice and under the command of the field marshal, line-up in Piazza del Duomo next to the cathedral.
Seventeen pairs of flag-bearers stop at the various points in the Piazza and in synchrony with the drum roll perform a spectacular flag-waving exhibition culminating with the throwing of the flag at the end.
The central focus of the procession is the passing of the Carroccio, the modern counterpart of the Republic's ancient triumphal chariot on which the silken colourful Palio banner is hoisted.
The Palio is hoisted on to the judges stand while the seventeen flag-bearers perform their own drum roll, "la sbandierata della Vittoria" (the flag-waving of Victory), so called because it was introduced at the end of World War I. Corteo storico (Palio di Siena) (Wikipedia in Italian)