What is Palio in Siena?
Siena palio are horse races held in Siena since 1656 (some sources give 14th century as a starting date). Although first Siena races were done with bulls and even with donkeys, later a definite switch to horses was made.
Palio horse race participants are chosen by a lot held in spring which allows only ten different Contradas to take part in palio of Siena. A certain number of Contrade have a right to participate in Palio "di obbligo" - for sure, without being selected by a lottery.
What are Contrade of Siena?
Contrada of Siena is a kind of historical local municipal government (neighborhoods) having a very long history. Siena is divided into Contradas for 800 years.
How are Siena Palio horses selected?
Palio horses are selected a few days before the event. All the horses must go through the test run (the tratta) in order to select 10 best horses for Palio races. All the 10 horses selected by a trial get a number written behind their ear.