Thousands of spectators gathered in the Tuscan city of Siena for a traditional bareback horse race around the main square. The Palio di Siena has been held in the Piazza del Campo in the centre of the medieval city, twice a year, almost without fail since 1656.

Palio di Siena horse race
Carabinieri officers ride their horses during a parade before the fifth heat for the Palio of SienaStefano Rellandini/Reuters

Siena is divided into 17 contrade, or parishes, and each enters a horse and a rider in the race, although only 10 make it to the finals. The parishes all have their own banners, jockeys' colours and mascots, dating back to the Middle Ages. The 17 parishes are: Aquila (Eagle), Bruco (Caterpillar), Chiocciola (Snail), Civetta (Little Owl), Drago (Dragon), Giraffa (Giraffe), Istrice (Crested Porcupine), Leocorno (Unicorn), Lupa (She-Wolf), Nicchio (Seashell), Oca (Goose), Onda (Wave), Pantera (Panther), Selva (Forest), Tartuca (Tortoise), Torre (Tower) and Valdimontone (Valley of the Ram).

Palio di Siena horse race
Andrea Coghe, jockey of the Selva (Forest) parish, rides during the fourth practices for the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
Jockey Giovanni Atzeni of the Istrice (Porcupine) parish rides his horse during the third heat for the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
Members of the Valdimontone (Valley of the Ram) parish attend a ceremony for the blessing of their horse Sarbana and jockey Jonatan BartolettiFilippo Monteforte/AFP
Palio di Siena
Giovanni Atzeni of the Istrice (Porcupine) parish shouts at Jonatan Bartoletti of the Valmontone (Valley of the Ram) parish at the start of the third heat for the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
The horse of the Oca (Goose) parish is escorted by a groom during a parade before the Palio di SienaStefano Rellandini/Reuters
Palio di Siena horse race
The horse of the Oca (Goose) parish is escorted by a groom before the second heat for the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
A Carabinieri officer crashes during their parade before the fifth heat for the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
Carabinieri officer lies on the ground after a crash during a parade before the fifth heat for the Palio of SienaStefano Rellandini/Reuters

The race rarely lasts longer than a few minutes, and the winner is determined by which horse – not which rider – crosses the finish line first. In 2010 the horse owned by the Selva (Forest) parish crossed the line without its jockey and was declared the winner. The winning parish is presented with the Cencio or Palio, a silk banner.

Only nine of the ten parishes that qualified for the final on Wednesday 16 August actually started the race, as the Lupa (She Wolf) parish was disqualified because their horse was injured. After a breakneck race in which at least one rider fell off, the Onda parish's horse Porto Alabe, ridden by jockey Carlo Sanna (known as Brigante) romped home in first place.

Palio di Siena
Carlo Sanna of the Onda (Wave) parish and his horse are blessed by a priest in the church before the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
Elias Mannucci of the Chiocciola (Snail) parish leads the Palio of Siena horse raceStefano Rellandini/Reuters
Palio di Siena horse race
The competitors round a bend during the PalioStefano Rellandini/Reuters
Palio di Siena horse race
Luigi Bruschelli of the Bruco (Caterpillar) parish crashesStefano Rellandini/Reuters
Palio di Siena horse race
Luigi Bruschelli of the Bruco (Caterpillar) parish falls of his horse during the Palio of SienaStefano Rellandini/Reuters
Palio di Siena horse race
The jockeys and horses of two different parishes vie for positionStefano Rellandini/Reuters
Palio di Siena horse race
Carlo Sanna of the Onda (Wave) parish wins the historical race on his horse Porto AlabeFilippo Monteforte/AFP
Palio di Siena horse race
Jockey Carlo Sanna, known as Brigante, celebrates after winning the Palio di Siena for the Onda (Wave) parish on a horse named Porto AlabeFilippo Monteforte/AFP
Palio di Siena horse race
Carlo Sanna of the Onda (Wave) parish celebrates with supporters after winning the Palio of Siena horse race on 16 August 2017Stefano Rellandini/Reuters
Palio di Siena horse race
Members of the Onda (Wave) parish celebrate with the winning jockey Carlo Sanna, known as BriganteFilippo Monteforte/AFP

Read more