Local people find original ways to prove themselves. In England, these are typically mild – such as chasing a rolling cheese down an uneven hillside. On the Continent, they are more macho. The Spanish have chosen bulls as foils for their virility – variously enraging them and running away from them. For the Italians, it is horses. In the hills behind Naples, you can still see a Campanian mountain boy standing up on two unsaddled horses and riding them like a pair of water-skis. He crosses himself before he mounts and – when at full gallop – blows a kiss to his spectators.

But Italy’s greatest display of equestrian bravura is the Palio di Siena. The Palio is a wilfully dangerous bareback horserace around the sharp bends of Siena’s three-sided Piazza del Campo, during which the jockeys’ whips double as weapons to unseat their rivals. It is unarmed cavalry warfare on a hard clay racetrack. If this sounds antithetical to a modern Italian, remember how long Italy was at war with itself. The Palio grew out of a tradition of martial games played on the Piazza to prepare the Sienese for battle – usually against their neighbours, the perfidious Florentines. A mystified Renaissance visitor recounts a huge ball being thrown from the Piazza’s 80-metre tower into the opponents’ half. A simpler game – simply called The Fight – was disbanded by the local bishop when the participants started stoning each other.

The intense competitiveness is catalysed by the city’s centuries-old division into districts: the contrade. Each contrada has all the grandiose accoutrements of a state – a flag, an anthem, a patron saint. Each field both a horse and a rider in the Palio. Because the horse is as much a representative of the contrada as the jockey, it may still win by crossing the finish line unmounted (many do). Thoroughbreds are forbidden. All the mounts are solemnly blessed at the altar of the contrada church on the morning of the race. By the evening, one will be treated to a hero’s retirement. Several will likely be injured or dead.

The event itself is considerably quicker than the fanfare surrounding it (apparently not uncommon in Italy). The record for the three-lap, one-kilometre distance is only 74 seconds. But for the preceding two days the contrade compete in an orgy of medieval pageantry unrivalled in Italy. The display nearly earned the Palio a place on UNESCO’s ‘Intangible Cultural Heritage’ list; had the Italian culture ministry not vetoed it on animal-welfare grounds

It is as well they did, for the realities of the Palio are very tangible. On the eve of the race, the city’s squares are closed as the contradioli sit down to banquets in their hundreds. These suck the life from the surrounding streets, which echo to the sound of unseen feasting. Tables are thumped and waves of song crash against the old churches and palazzos. It is impossible for an outsider to get so much as a cup of coffee. Every Sienese wears a knotted silk scarf to show the object of their loyalty. Tourists have taken to joining in the fun, blithely picking a scarf and throwing it around their shoulders – only to be taken aback by the ice-cold reception when they turn down the wrong street.

On the afternoon of the race, each contrade proceeds through the city, bearing its historical attributes. They studiously avoid one other before forming into a single procession towards the Piazza. In front of the black-and-white mass of the Cathedral, each contrada stops. To the sound of a snare-drum tattoo, the two flag-carriers turn huge square banners in ornate patterns. As the drummer reaches his crescendo, the flagpoles are presented and thrown high into the air. Among best contrade, they describe a perfect arc; passing each other at its apex before descending on the opposite number with the speed of a falling spear. They are always caught. Despite the applause, the spectacle is afforded total reverence: castigation awaits anyone popping a champagne cork at a parading Contrada di Siena.

The Piazza del Campo itself is in the shape of a spread cloak – pallium – representing the shroud of the Virgin Mary, in whose honour the Palio is run. The land slopes downwards towards the neck, meaning the second turn – equivalent to the corner of the garment – is a downhill right-angle. This is the corner of San Martino, which has claimed the most equine and human casualties over the centuries (the local website eagerly proves this by means of statistical analysis). In 1999, the Sienese grudgingly placed a hundred yards of plastic-covered crash-pads against the red Tuscan brick.

Steep wooden stands ring the track. For the practice run – which takes place on the eve of the race to acclimatise the horses – these are ordered by contrade. One bank is reserved for children, who sit in colour blocks singing their local anthems in a quick, high monophony. In the adults’ stands, the men sing pointedly towards their rivals across the Piazza – who sing back. For all the public rivalry, race-fixing is allegedly as venerated a tradition as the blessing of horses. The Sienese will deny this. Yet an old man, on being wished luck, shrugged and resignedly said: yes, but we’re not going to win this year.

On race day, the atmosphere is electric. The horses prance onto the track ridden by jockeys in the full-length colours of their contrada (the Tuscan impulse towards decoration is too great for anything else). They guide the hyper-sensitised animals into a starting pen marked by two thick ropes, each held taught by cast-iron devices built into the Piazza. It is – allegedly – within this bit-chomping, pawing mass that the last-minute deals and alliances are struck. The crowd noise mounts whenever the pack appears to be ready. The eventual start – signalled by a gunpowder explosion – is a vertiginous moment. To a spectator in the centre, it is as if the Piazza itself has swung into orbit. As the sound of the explosion fades, the low drumbeat of hooves on packed clay is nothing short of breath-taking. Whips blur on the rippling haunches before being brandished forwards like maces. The jockeys approach San Martino with a look of religious abandonment, hauling back on the reigns with their pyjama’d legs thrown wide. The Eagle contrada tries to pass the Giraffe on the outside of the corner. The manoeuvre is extinguished against the heavy cushioning but the pursuing jockey remains mounted. When a rider does go down, the crowd wows with fear and cranes to see if his colours resurface by the wall of the track. The horse will streak ahead in a low gallop; unreigned and beautiful, invisibly saddled by the hopes of its contrada.

Very quickly, it is over. A triple banger signals the finish, and members of the winning contrada flood the track in the path of the exhausted horses. The jockey fights them away in irritation until he can rip off his shirt and engage in proper victory celebration. The remaining horses are somehow recovered to safety. Rivalry dissolves and the other contrade descend on the winning district of the city to celebrate. The winners carry babies’ dummies to signify that they have been reborn in victory. But competition is never in abeyance for long. Unable to restrain themselves to a merely annual recrudescence of their old culture, the Sienese run a second Palio in August. They furthermore hold extraordinary Palios to mark great events. Formerly battles, these now tend towards world-historical moments – the end of World War Two; the Apollo moon landings; the centenary of Italian unification.

This year, the security presence was greater than usual. Large groups of the national riot squad – which doubles as an anti-terror unit – moved through the old city. One flooded a local café for their morning cappuccinos. There was a brief bag search to gain access to the course – an armed carabiniera quipped that the Palio is already dangerous enough without terrorism – but no visible infrastructure. Italians hint privately that the country has avoided an attack because the parallel structures of organised crime do not allow for one.

Despite the exaggerated local rivalries – or perhaps because of them – there was a striking lack of crowd management at the Palio. The people in the closely-packed piazza dispersed across the track and through a few small entrances within minutes. There was no littering. Within half an hour, the restaurants had laid out their tables on the hoof-beaten sand, and started serving dinner. Like the Tallin Song Festival – another lightly-regulated, monocultural blow-out – it was a bittersweet reminder that a self-regulating society is not only possible, but was once the norm.

The next Palio di Siena will be run on 16th August 2017