An Italian original

In a tiny church in the hilltop town of Monte San Martino in the Italian Marches, there's the most beautiful horse you've ever seen. It's the palfrey of an unnamed knight in an untitled painting. The knight sits on his saddle, warding off with his drawn sword the attentions of a bearded roughneck. The roughneck's fingers are on the horse's gold bridle, and the horse's mouth is curled into a supercilious half-smile, as if asking: "Who are you touching, asshole?" One of its eyes is turned towards the outrage. The other is more melancholy, as if the beast is resigned to the boredom of all the knighthood stuff, the display and derring-do, the golden impedimenta, the camp little tassel dangling on its brow... Stoic and amused, noble and ironic, the Smiling Horse is the most knowing painted equine I've ever seen.

In a tiny church in the hilltop town of Monte San Martino in the Italian Marches, there's the most beautiful horse you've ever seen. It's the palfrey of an unnamed knight in an untitled painting. The knight sits on his saddle, warding off with his drawn sword the attentions of a bearded roughneck. The roughneck's fingers are on the horse's gold bridle, and the horse's mouth is curled into a supercilious half-smile, as if asking: "Who are you touching, asshole?" One of its eyes is turned towards the outrage. The other is more melancholy, as if the beast is resigned to the boredom of all the knighthood stuff, the display and derring-do, the golden impedimenta, the camp little tassel dangling on its brow... Stoic and amused, noble and ironic, the Smiling Horse is the most knowing painted equine I've ever seen.

Its artist, Carlo Crivelli, is a patron saint of Le Marche. Born in Venice (c1435), where he studied under Mantegna, he was thrown into prison for adultery at the age of 22, and on his release turned his back on the Serenissima and went to live in the Marches, near Ascoli Piceno, for the rest of his life. His paintings are all of religious subjects, but are stylistically a million miles from the droopy saints and demure Virgins of the Renaissance. In their intense individualism, they embody the spirit of this previously undersold region.

For Le Marche has always lived at a slight angle to the rest of Italy. Stuck between the Apennines and the sea, it's always been a border zone, a wallflower at the dance of Italian history. Its medieval inhabitants were the Pope's tax collectors, hence the Italian saying, " Meglio un morto in casa che un marchigiano fuori della porto" ("Better have a dead man in your house than a Marches man at your front door"), and they've suffered from the association ever since. Ignored by their neighbours and by the big formaggios in Rome and Milan, the Le Marche towns were never turned into proper cities, nor did its fields get ploughed up for commercial development. Its most significant activity - shoemaking - is a cottage industry; more than 2,700 small factories supply Gucci, Prada and Versace.

In consequence, Le Marche is at first glance a region of mellow, rustic simplicity, a slice of old Italy that hasn't sold out to tourism, urban sprawl or mass manufacture. It's the vero Italia, without all the operatic song and dance. Which may be why it's not a holiday destination that's on everyone's must-go list. We found Le Marche by accident, while perusing a website called Traditional Tuscany and trying to find a villa that could take 12 people on holiday. Only four villas in central Italy could house such a throng, and one of them was in the province with the curiously French name.

We gazed at the map. Le Marche? It featured no towns or cities we'd ever heard of, except Ancona - that busy port through which I tutti Italia travels to the Greek Islands. And Urbino, which (now I remembered) once boasted a famous Duke and a matching palazzo. Apart from that, there seemed to be nothing but fields and hills.

We flew to Ancona from Stansted, drove down the coast, turned right at Civitanova Marche, and headed west towards the mountains. Our villa was huge, airy, modernised and classy in its anonymous way, surrounded by pear and fig trees, ferny bushes, old stone barns and the massive shoulders of Monte Rotondo and Monte Priora, twin stars of the Sibylline range. We suffered car breakdowns, rescues and traumatising electrical storms, but survived and spent a week idling blissfully by the pool, scorching in the 40C heat, making lunch, planning dinner, listening to teenage arguments (and to that moronic chav The Streets singing "Dry Yer Eyes Mate"), and playing endless games of charades in the evenings.

We were, for a while, stuck in neutral. Mostly, this was perfectly OK. Once you put in your mouth a dripping orange cube of cold, ripe Marche melon, and the slithery juice from its slimy crown has released its dizzy-making, honey-scented and (surely) alcoholic fumes into your brain, you feel there's no harm repeating certain experiences. At last, however, we went to explore Le Marche, the countryside beyond the grocery shops, and the region gradually unfolded itself. Seven-tenths is farmland. Driving through the winding roads and rolling hills, the state woods and nature parks, you take in big fields of sunflowers, poppies and purple heather, interrupted by little hill towns that feature the same grey walls, pink bricks and orange roofs. It was all gratifyingly ancient. The only concessions to the 20th century were the pylons and the two-lane superstrada that cuts across the region.

As undeveloped regions go, Le Marche teems with stuff. For one thing, it's got 180km of coastline. So you spend a day at the St Tropez-lite San Benedetto del Tronto, and another at the (smaller, gustier but much classier) Porto San Giorgio. Locals recommend the network of beaches outside Ancona; they're worth a look, but are of varying quality. Numana is distressingly full of Kiss-me-Kwik paraphernalia and crappy inflatables; Sirolo beach is beautiful, despite the off-putting metal bars on the boathouses.

The region also teems with churches, thousands of them, crammed with religious frescos and artworks. You cannot move in Le Marche for Madonnas, putti, haloed saints and the gastronomic free-for-alls of the ultimae cenae, or Last Suppers. Even the tourist board's promotional poster for Sernano is one of Crivelli's madonnas - this one a sulky tiara'd teen Virgin with her hair in corkscrew waves, her face set in a heavy-lidded frown, her amazingly long fingers holding a sprig of hyssop and a nastily spiked block of wood as she plans some act of menace against a young enemy.

You could explore the Marches in a kind of Crivelli crusade. His works aren't collected together anywhere; you have to look for them in churches all over the region - in Ancona, Ascoli Piceno, Corridonia, Macerata, Massa Fermana, Montefiore dell'Aso, Poggio di Bretta, Sant'Elpidio a Mare, and Torre di Palme. It's fun, but Crivelli-spotting requires patience. To see both the Smiling Horse and the Sulky Madonna, you have to drive to Monte San Martino, negotiate impossible bends on a one-in-two gradient, go past the church clock that is slewed drunkenly by 15 degrees, find the church of San Martino, locate the sacristan, wake him up and try to persuade him to let you look inside.

Your travels will take you to a dozen pink-bricked, honey-stoned towns where things are done in the old ways, as if you'd stepped into the Italian Cotswolds, only without the cream teas. San Ginesio, for example, is a charming walled town on a hilltop looking over the Fiastra valley. Its centre is laid out in a typically Roman cruciform plan. In the centre of the square is a looming statue of a Dante-esque figure radiating Catholic disapproval. Dominating the square is the spectacular Collegiata church, inside which sprigs of sunflowers decorate the ends of the pews, and underground is a crypt full of dramatic frescoes by Lorenzo Salimberi dating back to 1400. If you're lucky you can catch, in the summer months, the town's "reconstruction" (or copy) of the Palio, the terrifying bareback horse race that's held every year in Siena.

In Ascoli Piceno, the most significant city of the southern Marches, the Quintana is mounted every year - a spectacular jousting tournament that dates back to 1378. The place itself is pretty unchanged from Roman times; the beautifully-proportioned Piazza del Popolo is made of shiny stone called travertine which you're more likely to find in the Eternal City than in these bricky villages and towns. As a modern-ish corrective to the elderly arcades and palaces, check out the dark, sexy, Art Nouveau interior of the Caffe Meletti where they'll pour you a slug of home-made amaretto from one of the pale green bottles lining the walls.

Sarnano is a rather grand little town, with a fortified castle and a huge walled gateway, untouched for centuries, through which you walk up narrow windy streets to the Piazza Alta at the top. Two churches compete for the attention of the faithful: the renovated 14th-century St Francis, and the more appealing 13th-century Santa Maria Assunta which commands the high piazza, surmounted by a huge bell. Inside, amid surreal frescos, there's a Madonna of the People from 1494 (in which the Virgin Mary regards the viewer with an old-fashioned look, while two angels hold the edges of her cloak over a sheltering multitude of well-heeled sinners) by the German Pietro Alemanno. You walk back into town on polished cobbles, pausing at Pino's bar overlooking the mountains, where you have a Campari con arancia and try to imagine what the place is like in winter when there's snow on the slopes and all Sarnano goes skiing.

Living down the road, we began to treat the place like home. We discovered where to pick up the bread and almond tart, how to escape from the three generations of deranged women who run the supermarket, where to get the best ham, the best potatoes, the best-value wine. On market-day Thursdays, the square fills up with stalls selling household pots 'n' pans and cut-price foundation garments for super-sized local donna.

Nearby, Amandola has an imposing gateway and a pretentious pillared cloister in which to relax with your mid-morning macchiato, but has fewer treasures to offer. It is, on the other hand, the gateway to the Sibylline mountains, which are to Le Marche visitors what Helvellyn Crag was to Wordsworth - a stark phenomenon of nature amid all the peaceful, picture-perfect surroundings. We went Sibyl-hunting at the end of our vacation. After all the churches, the shrines and the atmosphere of slightly smug religiosity that characterises the region, it was a bracing experience.

The mountains where the Sibyl supposedly still lurks are alarming places. You know the Sibyl? Imagine a divine version of the vengeful, rabbit-broiling Alex Forrest in Fatal Attraction, and you're there. The Sibyl was one of a dozen wise female prophets who predicted the birth and death of Christ. The Cumean Sibyl of Campania - the presiding fairy of these hills - is a special case. She confidently expected God to choose her to be the bearer and mother of Christ, and when she was usurped by the Virgin Mary she abandoned her cave in Campania and flounced off to the mountains in Le Marche that had been respectfully named after her. Here, for centuries, she's supposed to have cast erotic spells over all who dwell in the mountains. Romantic tales and horror stories have abounded since the late 14th century. In their wake came hordes of bad-taste tourists after secret rapture, all heading for the lake around Norcia and the cave of the scorned almost-Madonna.

The Pope, exasperated by this rampant heathenism, ruled that anyone making a pilgrimage to the Sibyl's region would be excommunicated. But the appeal of the place continues. Why? Why do you think? It's the pull of Sin, the lure of the counter-Enlightenment, the appeal of transgression in this region of God-fearing sanctity...

You take the road to Montefortino and turn off where you see a sign to the national park. The roads grow steeper around Rubbiano, and you must stifle any impulse to get out and yomp the three miles to your destination. Stay on the serpentining road beyond Rubbiano, find a sign announcing "L'Infernaccio", park at the end of the rutted path, walk for 15 minutes and you'll get your reward.

You are suddenly standing, feeling very small, in a landscape straight out of Caspar David Friedrich. A dozen high jutting crags, randomly sprouting ash and beech trees, loom above you. Look down, if you dare, and see how the land falls away into the valley like a collapsed dance-floor. "A savage place," wrote Coleridge of the chasm in Xanadu, "as holy and enchanted/ As ere beneath a waning moon was haunted/ By woman wailing for her demon lover". He should have been here.

What holds the attention, and draws all eyes, is the Infernaccio. Translated as "The Shabby Little Throat of Hell", it's the tight V-shape where two mountains - Monte Sibilla and Monte Priora - converge. The eye travels down a 200ft fissure that looks like flesh split apart with a crystal waterfall tinkling from its secret interior. It feels indecent to be looking at this gigantic limestone vagina; you'd think the Sibyl had set out to seduce a mere mortal with this startling vertiginous display.

You can, if you have time, go right down the slope towards this narrow canyon, with the river Tenna crashing in your ears. Look up at the crags miles above you, and you can imagine how pilgrims could have thought they were heading for the courts of a very dominating and spiky goddess.

The pilgrims' destination was the town of Norcia, on the far side of the Sibylline mountains. When you go a-visiting there, you're not surprised to discover its murky and savage past. A chilly, gloomy, squat-looking town (since the 18th century, buildings were limited to only two storeys) perched on a high plain, Norcia is famous for three things: its pork butchers, its most famous son, St Benedict, the founder of western monasticism - and its castrati. Yes, this is the place where the parents of talented young male singers with unbroken voices would bring their unfortunate offspring. The boy would be drugged with opium and put in a very hot bath until he became unconscious, upon which a Norcian surgeon would sever the testicle ducts, guaranteeing the kid's voice would stay a screechingly high falsetto. Nice people.

The Italian Tourist Board is keen to promote the "unspoilt" qualities of Le Marche, recklessly drawing the attention of Eurotravellers to its pristine integrity, its heart-of-Italy authenticity, its hidden treasures. Soon the people who lable Umbria "the new Tuscany" will be casting greedy eyes on "the new Umbria", slightly to the right and down a bit. But don't be fooled by the smiling, inoffensive, humble-peasant face of the Marches. Behind the thousand churches, the cute small towns, the whited sepulchres of Travertine rock, there's an ancient wildness, a streak of non-conformity and waywardness you can feel in the atmosphere, behind the friendly grins and the willingness to oblige.

This is a place where wolves and bears roam the national park, where the madwomen in the supermarket urge enormous magic mushrooms on you, where the beach huts at Sirolo are barred like cells, where the Lago di Pilato - supposedly the lake where Pontius Pilate drowned himself after presiding over the trial of Christ - turns red every year, and where the sunflowers never seem to lift their heads to the sun but stand like disgraced militiamen, thinking of their terrible fate. Le Marche is a compelling mix of the ordinary and the spooky, the sacred and the profane, the smooth and the jagged. No wonder Carlo Crivelli's horse manages to look so bored and so wicked at the same time.

TRAVELLER'S GUIDE

GETTING THERE

John Walsh paid £240 return to fly from London Stansted to Ancona on Ryanair (0871 246 0000; www.ryanair.com). Fares are usually much lower in winter.

No other airline serves the airport from the UK; the other main gateway to Le Marche is Rome, which has flights from a wide range of British airports.

GETTING AROUND

Public transport in Le Marche is cheap but infrequent. John Walsh rented a Renault Mégane through Holiday Autos (0870 400 0010; www.holidayautos.co.uk). The price starts at £249 per week.

STAYING THERE

The villa that John Walsh and his party rented is the Il Gelso costing £2,400 for a week and sleeping up to 12 people. Details from Traditional Tuscany (01553 810003; www.traditionaltuscany.co.uk).

MORE INFORMATION

Italian State Tourist Office, 1 Princes Street, London W1B 2AY (020-7408 1254; www.enit.it)