Chilling: Amar Grover witnesses Buddhist ceremonies in a remote Himalayan valley

I was bound for Spiti, one of the Indian Himalayas' most isolated and stunning regions. Bordered by Ladakh to the north and Tibet in the east, the Spiti Valley lies at one of India's cultural frontiers, where Hinduism gives way to Buddhism. Closed to outsiders until 1992, it feels and looks more like Tibet and offers the traveller the chance to glimpse the Tibetan way of life while remaining inside Indian borders. The geography is impressive: nowhere is below 10,000ft and its peaks crest 23,000ft. Beyond reach of the summer monsoon, the sparse greenery of this upland desert reflects the harsh lives of its hardy people.

I was bound for Spiti, one of the Indian Himalayas' most isolated and stunning regions. Bordered by Ladakh to the north and Tibet in the east, the Spiti Valley lies at one of India's cultural frontiers, where Hinduism gives way to Buddhism. Closed to outsiders until 1992, it feels and looks more like Tibet and offers the traveller the chance to glimpse the Tibetan way of life while remaining inside Indian borders. The geography is impressive: nowhere is below 10,000ft and its peaks crest 23,000ft. Beyond reach of the summer monsoon, the sparse greenery of this upland desert reflects the harsh lives of its hardy people.

At nearly 15,000ft, Kunzum La (or pass) is one of two main gateways to Spiti. Prayer flags flutter about a small temple backed by a wall of peaks. This is a land of hilltop monasteries that have often served as fortresses. Ki Gompa is one of Spiti's oldest and largest. We had glimpsed it from afar, a cluster of pale cubic houses perched above the valley on a dun hillock. Now, at its walls, we climbed up into a tunnel which led to a courtyard and several beaming monks.

Founded in the 11th century, parts of this structure are almost as old. Ki is known for its thangkas: elaborate religious paintings framed by brocade and hung in several prayer halls. Within minutes we were shown flaking examples, their colours dulled by centuries of smoke and grime.

The Ki road winds on above a side valley up to Kibber village. Just where the valley narrows into a sheer canyon, steel cables were slung across to the far side and a pair of cradles hung over the abyss. Sometimes called flying foxes, they're a common sight in much of the Himalayas, especially by rivers, but I'd never seen one as implausible as this. It seemed only the bravest of villagers could crouch in those small cradles, pulling themselves across and praying the wind wouldn't rise. I was told later this particular set had never really worked and was far too ambitious, its government builders having ignored local wisdom.

At 13,800ft Kibber is reputedly the world's highest village. As we poked about its dusty paths in the sun, it was hard to imagine the intense cold which grips Spiti for eight months a year. Now, in the short balmy summer, Kibber's fields of barley glowed, their lushness all the more startling in such a stark landscape.

In Kaza, the market town of whitewashed houses that serves as the region's capital, our innkeeper wondered if I liked fossils: a speciality of his being a "fossil route". High above Kaza sits Thangyud gompa (monastery) and a string of tiny villages; one could, he said, easily walk on to Demul and the dramatic Dhankar gompa. We packed our sleeping bags, a few extra biscuits and set off next morning.

I felt like a fossil long before we found any. At this altitude, the steep path left us puffing and panting so we paused often to gaze across the valley at snowflecked peaks. At Thangyud an old monk briefly showed us the original maroon prayer hall. A stuffed, moth-eaten snow leopard hung inside the doorway and beyond lay a dim room of swirling frescoes and demonic statues.

The newer whitewashed building was more welcoming, with dozens of monks' rooms lining a large courtyard. Since many had gone home to help with the harvest, we were given a spare room. It was neat and cosy, with a kitchenette in one corner and a futon in another. Later I watched a regal Lama canter off into the hills on his horse. There had been a death nearby and he was required for the last rites.

Hissing pressure cookers heralded dinner. Our monk hosts had prepared true hikers' fare: a vegetable stew less frugal than the usual monastic meals. We gorged on apricots and creamy yak curd.

A chill dawn gave way to a hot day. On the trail to Demul I found a fossilised shell and cheery shepherds hailed us from their rock shelters. Mani walls - carefully piled stones engraved with prayers or Buddhist symbols - ushered in the village. Its dazzling pale homes rose in tiers above a patchwork of fields and the silence was broken by crashing cymbals and groaning horns. We traced this cacophony to a large house and within seconds were pulled upstairs.

In one room sat a dozen musical monks and on a kind of plinth sat the horse-riding lama. So these were the last rites. Before I could even feel like an intruder, a plate of snacky things was placed before us on a rug. The chanting and bizarre orchestration droned on. Just when it seemed some monks might nod off they'd suddenly perk up and belt out a few bars. At the interval we all headed for the roof, and I asked when they'd be done. "Two more days," sighed one and, seeing my surprise, he added that their monastery would be paid.

A monk's family put us up, kind but poor people with snotty-nosed children and cracked panes that rattled in the windy night. Next morning we trudged on across barren hills and finally gained a ridge on whose pinnacles clung Dhankar.

There is no more stirring sight in Spiti than Dhankar's gompa and fortress. The name means "mountainous place inaccessible to strangers" and it was here that Spiti's old rulers made their capital. From here beacons could be lit to warn villagers of danger, for this tiny kingdom was often caught between competing neighbours' battles.

While this is Spiti at its most dramatic, the real treasure house lies 19 miles east at Tabo. Four years ago Tabo monastery celebrated its millennium with pilgrims, the Dalai Lama and Richard Gere. By Himalayan standards its setting on the valley floor is tame, yet the ancient mud wall encloses a compound an acre and a half in size. Within stand at least 20 shrines and nine temples whose murals and stucco sculptures have long thrilled Buddhist art historians.

Legend claims it was built in a single night, and archaeologists reckon some of the most skilled Kashmiri artisans beautified its walls. Celestial themes and episodes from Buddha's life fill the gloomy, atmospheric halls. The Temple of Enlightened Gods resembles a kind of cosmic map while another was once reputedly covered in gold leaf. Ferocious deities are depicted with skull rosaries, tiger skins and flaming halos, and a local guide is invaluable to make sense of the iconography.

Days later, that arcane world of spirits and demons was brought to life at a monastery festival in the nearby Pin Valley. Known for its ibex and even snow leopards, we watched far stranger creatures in the form of monks performing elaborate dances. In lurid monster masks, brandishing knives or drums, they skipped and twirled round a courtyard. An enthusiastic crowd of villagers, clearly in carnival mood, followed every move.

This was Spiti at its most exuberant and colourful. Most gompas have annual festivals yet despite the dancing, music and drinking, they're not merely frivolous affairs. We watched a horned dancer tease a fleshy slab of tsampa dough; drums rolled, the crowd gasped and down lunged his knife. Now it lay in pieces, the symbolism clear - even up here in the remote Himalayas, good triumphs over evil.