The Palio! I like Siena a lot, and have studied and lectured about the Campo, my favorite piazza, but I'd never go to the palio since I'm not great on being stuffed into very crowded situations. The palio is a 90 second race that has been run for many centuries; not easy on the horses or riders. It's the horse that wins for its contrada (district) since riders sometimes fall off. Actually there are two races, two different feast days when it happens.
"Jockey Luigi Bruschelli competes in a horse race in Del Campo square, Siena, Italy. Riders compete bareback in a bid to win the Palio, a silk banner depicting the Madonna and child."
Photograph: Stefano Rellandi/Reuters/via the Guardian