It has been described as "the world's toughest horse race" (BBC); "the greatest horse race in the world" (GQ); and "easily the most exciting 90 seconds to be had in all modern Europe" (The Guardian). For countless tourists it has provided the experience of a lifetime; yet for many animal rights activists it is an archaic monstrosity, responsible for the death of 50 horses since 1970. However you view the Palio of Siena, there can be no doubt that this is a totally unique event: a horse race that defines the identity of a city and, for 55,000 fanatical Sienese, serves as the embodiment of life itself.

You might have encountered the Palio. Every summer, newspapers publish various articles and photo essays in an attempt to shine a light on this strange Italian tradition. Well, up to a point: the features tend to describe the Palio rather than explain it. For the Palio is a very difficult thing to explain. Books have been written trying to decipher it – La Terra in Piazza: An Interpretation of the Palio of Siena probably goes deepest – so packaging centuries of history and culture within a mere 1,500 words may prove optimistic.

The salient points are these: the race is ridden bareback three times around Siena's central square, the Piazza del Campo. Ten of Siena's 17 districts, or contrade, compete in each Palio; the seven non-participants automatically enter next year's iteration (three are drawn by ballot). And once the race starts, anything goes: whipping your rival isn't only acceptable, it's encouraged. Think war – on horseback.

Of course there's more, much more: such as the partiti, the secret dealmaking that occurs between the contrade in the lead-up to the race, and continues between the jockeys as they jostle at the starting rope. Or the enmity shared by certain contrade (Aquila and Pantera, for example), a hatred so intense that a contrada would sacrifice a shot at winning the Palio to ensure their rival fell short. Or the suspicion a contrada often feels toward their jockey, the outsider hired for the race, the mercenary who might well easily betray them.

Even the scheduling of the Palio – twice a year, on 2 July and 16 August – appears somewhat bizarre. Why stage the races a mere six weeks apart? (To honour the Virgin Mary: the Visitation in July, the Assumption in August. Although, happily, the dates also ensure every contrade races at least one Palio per season.)
Rather than seek to explain the Palio, let us consider what it is that makes it wonderful – not only as a spectacle for the tourist, but also as a celebration of civic identity. In Siena, there is the Palio, and then there is everything else.

people belong to their contrada first, and siena second

One of the great appeals of the Palio is Siena itself: let's be honest, were the race held in Milton Keynes it's unlikely the tourists would come flocking. Stage a festival of colour under the Tuscan sun, within a medieval city so meticulously picturesque it might have been designed by Wes Anderson, and suddenly the world starts paying attention. Not, it must be stressed, that Siena particularly courts this attention: the city is fiercely protective of the Palio's integrity.

Unless you hail from one of the contrade, you can only ever experience the Palio as an outsider. This is the most beautiful aspect of the Palio, and also the most heartbreaking.The evening before the Palio, each contrada – even those not participating – gathers together for a communal dinner. Rows of wooden tables fill the largest square in the district; great quantities of meat and pasta are prepared by volunteers; seemingly endless bottles of wine are distributed; and, beneath the night sky, the people of the contrada eat, drink and discuss the race to come. It's hard to overstate the importance of the contrade to the people of Siena; an individual belongs to their contrada first, Siena second.

Outsiders can purchase tickets for these dinners, although there aren't many available. If offered the chance, attend one: not only will you remember the evening for many years to come (provided you don't overdo the vino), you should also form a bond with your host contrada that means you have someone to root for. Nobody should watch the Palio as a neutral.

Last August I attended the dinner of Aquila, the Eagle. Aquila hadn't won the Palio since 1992, the longest of any contrada. In Siena, such a contrada is known as the 'nonna', the grandmother; Lupa, the previous nonna, won the July Palio and thus passed the unwanted title onto Aquila. If that weren't enough, Aquila also holds the least victories of any contrada – a mere 24. (The record is held by Oca, Goose, with a cool 62.)

Yet that August the new nonna had a real shot. Their horse was considered quick. Their jockey, a dashing young Sardinian named Giovanni Atzeni, had won the Palio for Selva contrada the previous year – his fifth Palio victory. And some shrewd dealmaking in the July race – when cursed with a weak horse – had left Aquila with favours to call in.

Giovanni sat on the top table, flanked by the leaders of the contrada, the yellow helmet of the Aquila jockey placed in front of him. He appeared relaxed, shaking hands with the people who came over to wish him success. Later, he made a brief speech in which he promised to do his best to bring glory the next day. The affection is real but fragile. Failed jockeys are sometimes beaten up by their contrada, especially if treachery is scented or a rival is allowed to triumph.

As the evening wore on, plates emptied, yet more wine bottles were poured out, and the mood grew celebratory. A crowd formed in front of the top table, and the people of Aquila began to sing. It was a beautiful sound, that song, proud and sad, summoned by hundreds of voices in defiance of 24 desperate years that might finally be over. Some laughed, some wept; one man sobbed uncontrollably as he embraced his companion. All across the city, similar scenes would be taking place – although perhaps nowhere with such fervency as Aquila.

Watching the Palio offers various options. The most memorable – and expensive – is to hire a balcony of one of the apartments overlooking the piazza. As well as the race, you can see the preceding parade of the contrade – which involves drummers, flag throwers and mounted knights, all decked out in medieval pomp – from a comfortable vantage point. As the parade lasts many hours, comfort is recommended.

Alternatively, join the multitudes crammed into the centre of the piazza. If you arrive early enough, you can stand right against the barriers; but be warned, you will also face a long, sweltering wait, and only be able to see a small section of the track.

Although many Sienese attend the race, most prefer to watch within their contrada. In the streets of Aquila, the confidence of the previous evening has curdled into nervous, albeit excited, anticipation. Surely this is the moment? Surely not again…

Where to stay

Palazzo Ravizza

The Grand Hotel Continental Siena is unquestionably the most opulent hotel in Siena, but may we be bold enough to recommend the Palazzo Ravizza as a more understated option. An independent hotel, it has been run by the same family for more than 80 years, and each room is uniquely furnished.

At 7pm the horses emerge from the courtyard of Palazzo Pubblico, the great town hall that towers over the square. Lots are drawn to determine in what order the horses will line up before the rope. To the despair of its citizens, Aquila is drawn to start alongside its rival, Pantera (Panther). Sabotage seems inevitable.

The race is an anticlimax. Giovanni starts badly, and the horse is unable to make up the distance. He finishes several lengths behind Lupa – the same winner as July, and the same rider. After a 27-year wait, Lupa have two victories in six weeks.

After the race, pandemonium. The people of the victorious contrada race to the Duomo, Siena's great cathedral, where the celebrations begin. The black and white banner of Lupa is everywhere – you would think it the colours of the city. Into the Duomo, eventually, comes the horse, the triumphant jockey, and the Palio banner itself. (Each banner is unique, and kept by its victor – a new banner will be designed for July.) By now the cathedral is packed, stifling hot, echoing with cheers and the drumbeats that will last until dawn. A forest of camera phones block the view.

On the streets of Aquila, desolation reigns. Old men talk sadly on the steps, perhaps wondering if they will ever see another victory. Two teenage boys drift along, their arms draped around each other's shoulders in a gesture of solidarity and despair. Ten long months until July.

This is the side of the Palio few tourists will ever see. The quiet anguish, the broken hopes, a sorrow akin to mourning. As the Sienese have said: 'we do not play the Palio, we live it!' For better or worse.