The Palio is a complex event organized by the City of Siena.
Ten Contrade out of 17 run the Palio on 2 July, the sects that did not run the Palio in July of the previous year, to which three were added, drawn among the ten who ran it.
The draw takes place on the last Sunday of May. Similarly for the Palio of August 16, with a draw of the three on the first Sunday after the July Palio.
The 10 Contradas participate in the Palio race with a horse that is assigned to them by drawing lots from a selection of horses selected from those physically suitable.
Eligibility tests and horse assignments take place 3 days before the Palio (on the morning of 29 June and 13 August respectively for the two poles); before the Palio there are 6 trial runs (one in the morning and one in the afternoon) during which the jockey (chosen by the Contrada) becomes familiar with the horse.
You can watch the trial runs and the Palio by paying at the tribunes (boxes) arranged around the Piazza or at the windows and balconies overlooking it, or for free from inside the Piazza.
The Palio race is preceded by a procession (Passeggiata Storica) with over 600 participants representing the 17 Contradas and institutions of the ancient Republic of Siena. The procession starts from the Piazza del Duomo in the early hours of the afternoon, and winds through some streets of the city center before parading in the Piazza del Campo.
The actual race consists in traveling three times around the Piazza del Campo, properly arranged and equipped for the purpose, mounting the horse by hair (without saddle).