Siena has a total of 17 Contrade (districts http://www.aboutsiena.com/Palio-races-of-Siena/the-contrades-of-the-palio-of-Siena.html ). There will be 10 Contrade represented in the race on August 16. Seven of the Contrade in the race will be the Contrade who were not represented in the July 2 race. The other three will be chosen by lot from the ten who raced on July 2. The next race on July 2, 2018 will have the seven Contrade not in the August 2017 race and three other Contrade chosen by lot from the August 2017 race and so the rotation goes with each Contrade being assured to be in at least one race per year. Each Contrade has chosen its jockey, but has no idea of the horse it will be assigned until the lottery three days before the race takes place. Meanwhile each Contrade will spare no expense (it is estimated hundreds of thousands of Euros will be spent) in jockey salaries and select payments to opposing jockeys as the Cantradas position themselves to assure a win (http://www.telegraph.co.uk/films/2016/06/29/the-palio-is-life-what-a-corrupt-horse-race-says-about-italy/).
On our first night in Siena we were escorted through one of the Contrade districts with an explanation of the race and it significance. Each Contrade has its own hall/church/museum celebrating their history in the 400 year old race where they display the banners they have won, pictures of winning jockeys and horses, medieval uniforms. We received a classic Tuscan dinner in the hall, toured the museum, and listened as our guide explained the significance of the race while we sat in the sanctuary of the Contrade church where the horse will be blessed before the race. The stable stall where the horse will be pampered for the three days leading up to the race is more elaborate than the stables I remember from my days in the horse business.
Before the race begins the circumference of the Piazza del Campo is packed with hard clay for the horses footing. The celebrating by the Contrade starts about four days beforethe race with parades of drums and flag waving within all the Contrade. The lottery where the horses are selected is another big celebration. And there are six practice races leading up to the final race.
Essentially it is a four day festival held in July and August.
The other issue I found attention-grabbing was the crime rate in Siena, which uncommonly low, and is attributed to the influence of the Contrade and the horse race. https://dreamdiscoveritalia.com/2014/08/11/siena-Contrade-life/ Each Contrade is almost an island to itself located within the city of Siena. The Contrade is a home to the people who live in it with its members being citizens of the Contrade first, Siena second, Tuscany third, and Italy fourth. The only way to become a member of a Contrade is to be born into it, with an accompanying baptism similar to becoming a member of the church. Once a person is a member of a Contrade they will always be a member, to the point where marrying outside of the Contrade is similar to marrying outside of the faith. The Contrade establishes strong rules and guidelines based on tradition for its citizen’s behavior inside and outside the Contrade,