It is a long, lonely climb up the mountain from the medieval walls of Norcia, but worth the effort: at the top is a sight so strange that it verges on the mystical.

As the road crawls up through oak and chestnut forests, ridge upon ridge of blue Apennines opens up on the horizon until the whole of soft, green Umbria seems to be spread out below. Suddenly, the road jumps over the mountain's back and drops you on the edge of a vast grassy bowl, smooth as a carpet. A ring of bald white mountains rises all around. You have reached the Piano Grande.

It is like stepping into a dream. The air feels cool. In the pale green light, the only sound is the warbling of hundreds of skylarks. A tiny, white hilltop village shimmers in the distance.

We gawped at this vision, but the only other visitors present were not so overcome. A noisy carload of Spaniards drove up and tumbled out on to the roadside, each weighed down by a substantial camera. Ignoring the view, they photographed each other loudly before clambering back into the car and roaring off.

Luckily, the Piano Grande ('great plateau') doesn't figure in many guide books, or even maps. It was once a huge lake, a mile above sea level, but its waters have long since drained into the limestone below, leaving a rich mountain pasture. From its floor rise the Monti Sibillini - home to a mythical Sybil - a harsh range of the Apennines whose highest peak, Monte Vettore, reaches an Alp-like 2,478m.

This is where the gentle mountains of Tuscany and Umbria, so beloved of English tourists and incomers, give way to something altogether more savage and less welcoming. Behind you lies Umbria; its gentle landscapes, medieval towns and monasteries reproduced in a thousand paintings and frescoes. Ahead rise the first mountains of the barren south. The change in landscape reflects an economic and cultural divide: the lush, prosperous centre of Italy ends, to be replaced by the poor Mezzogiorno, whose centuries of poverty and isolation are not over yet.

Having climbed up to this place, the logical thing to do is set out, preferably on foot, across the miles of grass towards Castelluccio, the village on the other side. The walk takes the best part of a day and is likely to be one of the most solitary in your life.

During our crossing of the Piano Grande, we saw no one - on land that is. There were plenty of people in the sky. A large group of paragliders performed silent aerobatics above, like a flock of huge, weird birds, before floating down to the plain and disappearing.

Unusually for Italy, a country that is shooting-mad, bird-life thrives on the Piano Grande, partly because it is so remote and partly because the Monti Sibillini are a national park. Hooded crows, smart in their grey and black uniforms, flap clumsily about. Wagtails, pipits, larks and wheatears are everywhere. At one point, a falcon launched itself vertically off a mountain ledge.

The deeper you go into the Piano Grande, the more the landscape and silence envelop you. Its legends seem closer. The Sybil is probably watching from the barren slopes above as you trudge along.

This particular Sybil was condemned to live until the end of the world in the Grotta della Sibilla, on the mountain of the same name. The cave is the mouth of Hell itself, leading over an abyss and to a door guarded by dragons - allegedly.

During the Middle Ages, when the region was part of the papal states, the cave had a reputation as the place where pilgrims from northern Europe, journeying to Rome, were led to perdition. Why, in order to reach Rome, they should travel along the top of an almost inaccessible mountain has never been explained.

At the top of Monte Vettore is a tiny lake, haunted by the devil. Another legend says that Pontius Pilate, tormented by guilt after the Crucifixion, committed suicide after requesting that his body be carried into the wilderness on a cart drawn by wild oxen. When they came to Monte Vettore they plunged into the lake and sank for ever. Even now the lake periodically turns blood-red - though the prosaic explanation is the tiny crustaceans which live there.

With its miles of close-cropped grass, the plateau may look bare but is not as barren as it seems. Its damp pastures are rich enough to support cattle. Curiously, too, it is famous for green lentils grown, it is said, at a higher altitude than any others in Europe. They ripen slowly and are much prized by vegetarians. Another local cereal is farro, a fine, ancient strain of wheat grown by the Etruscans and still used in the region's traditional cooking.

When we reached Castelluccio ('The Little Castle'), it was not so much sleepy as in a deep coma. The people of the Piano Grande obviously take their siesta seriously. The steep streets of stone houses clustered around the little Romanesque church tower seemed devoid of life in the afternoon sun. Even Italy's ubiquitous motorini, the deafening, demon mopeds, were silent.

For centuries Castelluccio's church bell used to toll its warning to travellers on the plain when bad weather was on the way, guiding them to safety. Mountain mists can descend suddenly, and the Piano Grande can have heavy snow, making it a treacherous place.

In the Middle Ages, travellers regularly became stranded in the snow. Having to tramp out and rescue them became too much for the long-suffering residents of Castelluccio, and for a time travel to the plateau was restricted.

Perhaps it is best to restrict your own stay in such a place, too, for after a while the solitude and bareness can become wearing. It was with relief that, late in the afternoon, we climbed over the Piano Grande's northern lip (we had crossed from the south) and down into the Val Nerina, the long, deep valley that leads, eventually, to the river Tiber.

By evening we were back in the 'real' Umbria, drinking cold wine in the twilight, with scented woodland all around. It was hard to imagine that, high in the mountains, night was falling on the mythical meadow.


Getting there: The nearest airport is Rome. Alitalia (071-602 7111) and British Airways (081-897 4000) fly every day. Fares from pounds 210 to pounds 270 return plus pounds 6 tax. Cheaper charters may fly to Ciampino, Rome's second airport. Train from Rome to Spoleto takes about 1 1/2 hours, costs about 7,000 lire ( pounds 2.90) one way; and bus over the last 30 miles to Norcia (a further hour or so).

Organised Tours: The Alternative Travel Group (0865 310399) specialises in walking tours, including Umbria and the Piano Grande. Food, wine, accommodation and experienced guides are provided, as is motorised transport to the end of the day's walk, should your legs give out.

Further information: The Italian State Tourist Office, 1 Princes Street, London W1R 7RA (071-408 1254).

(Photograph and map omitted)