The roof of the world is a crowded place - crowded, that is, with the ultimate mountain range, rather than tourists. Harriet O'Brien, below, found no other visitors to Sikkim; Graham Hoyland, opposite, took some with him to Bhutan
Getting to heaven is literally an uphill task. Or so it seems in the Himalayan state of Sikkim, where monasteries are perched sublimely at the top of tall, forested hills. Spiritually, there's a quick way of finding out how you're doing in the heavenward stakes once you've huffed your way up to Tashiding gompa (monastery). This is one of the most sacred Buddhist monasteries in the small, serene-looking country whose recent history has seen it swallowed up as part of north-east India. Here, you simply follow the groups of monks and ladies devoutly spinning their prayer wheels as they perambulate the monastery and its outlying walls. Then you reach a well-marked point. You stand on one side of the path, close your eyes and put your index finger out. The trick is to walk across the path, still with your eyes closed, and place your finger in a significant hole in the wall. If you hit the spot you're well on the way to heaven. I tried, three times, but at each attempt ended up at a lower indentation. A sort of lesser purgatory perhaps? "It's just a bit of fun," laughed one of the monks who had gathered to watch these familiar antics. "Better luck next time."

At any rate, when you're at Tashiding you feel you're a good half-way to heaven. There you are near the foothills - itching with orchids - of the world's third-largest mountain, Kanchenjunga, amidst avenues of fluttering prayer flags. Butterflies flit past the neatly whitewashed stupas while sociable dogs amble lazily by your side.

On my visit, cheerful, maroon-robed monks emerged blinking into the bright sunshine having taken a break from their chanting and horn blowing in the richly painted main hall. They had gathered to pray for the Dalai Lama's trip to Taiwan at the end of last month. Although they follow a different sect of the Tibetan branch of Buddhism, the monks were deeply concerned about the political, as well as spiritual, ramifications of the Dalai Lama's journey. But that didn't cloud the courtesy and sense of fun there. We were offered mugs of Tibetan-style tea, a salty concoction served with splodges of butter, and as we sipped our way through the oleaginous brew, a deaf-and-dumb monastery helper mimed, with evident amusement, his own efforts over the hole in the wall. He had been more successful than me.

Visitors come to Sikkim largely to see the colourful gompas, getting a glimpse into a surviving enclave of Tibetan Buddhist culture; to admire the spectacular scenery of snowcapped mountains, trailing waterfalls, fantastical ferns, flowers and more; and to go trekking through the unspoilt peaks and valleys around Kangchenjunga. They find themselves in a land of easy-going good humour, a place with infinite nuances of delicacy and politeness. It is a world away from the hustle and hassle of neighbouring West Bengal.

Of course you know you're on your way to a distinctly different region from the red tape involved in reaching Sikkim. The Indian government has designated this a restricted area, and tourists need a permit to get there (see below). Paperwork in order, your starting point is Siliguri. This is the main trading point in Bengal for traffic from Darjeeling, Sikkim and the kingdom of Bhutan. From here you board a bus or hire a taxi-van and gradually twist your way up into the clean greenery of the mountains. Gangtok, the Sikkimese capital, is about three and a half hours away.

The sharp twists of the mountain road are painted with signs in English encouraging safe driving - "Be gentle with the curve" and so forth. Towards Gangtok the signwriters had got carried away with their own moral rectitude: "If you judge people you won't have time to love them" was emblazoned on a particularly perilous hairpin bend. "Imagination is better than wisdom" said another, as if challenging drivers not to get distracted by pondering quite what this means.

The mottos are painted by a branch of the Indian army whose job it is to make and maintain the roads. And there is a great deal of military activity here: Sikkim is a sensitive area, you are informed, because of its border with Tibet.

Indeed, travelling north to Yumthang, a particularly high and beautiful valley about a day's drive from Gangtok, you pass truckloads of khaki vehicles and squads of crisply laundered soldiers. As the area is only about 35km from the Tibetan frontier, visitors need (another) special permit to get there and are not allowed to bring cameras. We spent the night at the nearby village of Lachung and got up at dawn the next day to catch the mountains at their best, snowclad peaks glowing in the early- morning light. As we drove up to the valley through a trio of army checkpoints, a Sikh contingent was out on exercise, doing press-ups by the side of the road - turbans neatly in place, moustaches immaculately twiddled and not a hair out of place, despite their exertions. I couldn't help wondering if the corresponding Chinese border guards were as wonderfully well groomed - and numerous.

A Chinese threat is certainly a reason for Indian government sensitivity over Sikkim, but by no means the only one. "In 1959 the Chinese invaded Tibet," I was told at one monastery. "And in 1975 the Indians took over Sikkim." There was much international criticism at the time. For centuries, Sikkim had been a proud, independent kingdom and its chogyal, or ruler, embodied a leadership that was intertwined with the spiritual history of the nation. The Indians took over in the name of democracy that en route was translated into union with themselves.

Their recent political involvement started in 1947 when, on independence, they inherited British treaties with Sikkim - largely over border control. Although during the 1962 Sino-Indian border wars the Chinese respected the frontiers of the Himalayan kingdoms of Nepal, Sikkim and Bhutan, the Indians were left deeply suspicious. By the early Seventies the government of Indira Gandhi was displaying distinct designs on Sikkim. And in 1975, amid democracy demonstrations in Gangtok, the Gandhi government imposed a referendum with the result that Sikkim was annexed as the 22nd state of India. The army surrounded the chogyal's palace, stripped him of his powers and placed him under house arrest for two years.

Accusations flew that the Indian government had simply imported the demonstrators from Bengal, had considerably swelled the population with a flood of foreign workers (who had little regard for the independence of Sikkim), and had in any case rigged the elections.

Mass immigration had, in fact, been started last century by the British, who introduced a large wave of Nepalese labourers. The Indians continued the practice and the number of incomers continued to rise, dramatically so after 1975. Today the Sikkimese amount to less than one-quarter of the population of their own country. And heavenly though the Sikkimese monasteries are, Buddhism, too, is in the minority - about 60 per cent of the population are Hindu.

Yet for the Sikkimese, the outlook is not entirely bleak. If their culture is to survive, so must their religion and their monasteries. And to this end the current chogyal, who inherited his father's title (but not his former political power) has set in train a movement to revive and preserve Buddhist practices. Meantime the Sikkimese themselves keep an interested watch on matters in neighbouring Bhutan, which has recently seen a similar tidal wave of incoming immigrants. "The Bhutanese have been very frightened by what happened to us," I was told in Gangtok. "In terms of demographics?" I wanted to know. "Not just that. Ultimately, there's always the possibility of another takeover."