Ever since I can remember, I have known of Tso Ngon, the Blue Lake of Amdo - known also as Koko Nor in Mongolian and Qinghai in Chinese - Tibet's largest lake and one of its most sacred. Like a corollary to Kumbum Monastery as the mythical symbol of my ancestral roots, Tso Ngon loomed large in my imagination as a child. Growing up in the north Indian hill station of Darjeeling, I had always thought that Kumbum and Tso Ngon were somehow related, almost as if the monastery was situated on the shores of the lake. I realize now, coming to Kumbum, that the reality is something quite different. Although the distance between the two places is not great - a few hours drive - a more significant geographical and psychological barrier separates them: Tso Ngon is on the northern edge of the Tibetan Plateau, that great expanse of highland that defines the essence of Tibet; it is nomad country inhabited primarily by Tibetan-speaking Amdowas, whereas the region around Kumbum is considerably lower and agrarian and except for a minority Tibetan population, almost entirely occupied by Chinese and Hui Muslims.

After a few days at Kumbum, my wife and I hire a clapped-out taxi in Rusar, the largely Chinese town that surrounds the monastery, to take us to Tso Ngon. The Chinese driver - a sad shell of a man, lugubrious in his thick-rimmed spectacles - seems petrified of driving and sits hunched over his steering wheel cranking the car along at a snail's pace. For no discernable reason he drives for long stretches on the wrong side of the road until the wail of horns from oncoming lorries snaps him out of his catatonic state and forces him - just in time - to weave out of a head-on collision.

The road is broad and well-maintained; this is the main highway to Lhasa. The railway to Golmud follows us and for miles track and tarmac snake their convoluted way through narrow valleys and gorges, ascending all the time. A thick fog engulfs us and makes our driver even more nervous; he cranes his feeble neck forward in an effort to see better, his hands glued hard to the steering wheel, the knuckles standing out in stark relief. Soon we are above the tree-line. The fog lifts but the skies are lowering and dark with menace. There is no doubt that these surrounding hills were once grazing land but now their smooth, treeless sides have been stripped of pasture and carefully ploughed - a patchwork of fields clinging onto impossibly steep slopes, pocked by the familiar, inverted V hay-stacks that look at once mysteriously beautiful and depressing.

Barely three hours out of Kumbum and we approach Do Nyida - The Stone of the Sun and Moon - the pass that marks the geographic boundary between the Tibetan plateau and the lower Xining region. The road gradually levels and now, at last, we are surrounded by gently rolling grassland. Twin pagoda-like structures mark Do Nyida, symbols no doubt of the sun and moon. They are gaudily painted and must have once been intended for tourists but are now locked up and in disrepair; the main highway loops off in the distance skirting this point. A nearby hillock is topped by a huge cairn from which hundreds of prayer flags sprout, fluttering loudly in the whipping wind. From here we can see the beginning of the Tibetan plateau, a treeless expanse of undulating grassland broken by irregular lines of mountain ranges. As if to beckon us, the low ceiling of clouds that has hung over us throughout this journey - mirroring the dark confusion of my emotions - magically breaks in front of us and gives way to a deep, shimmering blue that recedes infinitely into an otherworldly brilliance, not unlike the horizons in Renaissance paintings where the ghostly traces of trumpeting angels can still just be discerned, pregnant with the promise of enchantment.

We pass a market town, all concrete and functional. It is crowded with nomads who have come on horseback or on motorcycles with seats draped in saddle rugs. This is the first time since our arrival in Kumbum that we are seeing traditionally dressed Tibetans in such large numbers. The men wear dark woollen gowns loosely tied at the waist, their silver-sheathed daggers casually but prominently swinging from their hips, their entire demeanour cheerfully cocky and full of swagger. The women look even more traditional in their multiple braids and their full-length gowns, adorned with chunky pieces of turquoise and corral jewellery. The market is laid out on the dusty grounds of a small square. The wares on display are mostly cheap, manufactured goods - colourful clothing, electronic items, pots and pans, and other household products. A loudspeaker on top of one of the roofs broadcasts the distorted soundtrack of a Chinese action video being screened inside and its bloodcurdling sound-effects - grunts, screams and bone-crunching thuds - injects a sense of urgency into this otherwise placid scene.

We leave the market behind. The sky is now inky blue and viscous. The highway bisects the flat, sun-dappled plateau and vanishes into the far mountains that seem to float above the horizon. And then the lake appears in front of us like an optical illusion - so unexpectedly it might have been there all along - a clear blue band of water suspended between the sky and the golden, treeless earth. Tso Ngon! All around the lake, shadows lengthen along the nooks and crannies of grassy hills, their tops already flecked with the first snows and their slopes spotted with enormous herds of yak and sheep. A large stupa - luminous in the late light - stands on the shore, next to the crumbling ruins of what had once been a labrang - the household of a high lama. Powerful, uncontrollable emotions well up inside me, all mixed up but primarily, a kind of deep and ineffable happiness.

At an altitude of 3200 metres and situated on the edge of the northern Tibetan plateau, the lake is 360 kilometres around its circumference. Throughout history it has been venerated and worshipped, not only by Tibetans but also by the Chinese and Muslims who made blood sacrifices here as recently as the early part of this century in the belief that the unpropitiated spirit of the lake would otherwise cause the waters to breach their natural barriers and flood the lowlands around Xining.

We are invited for tea by a nomad family whose adobe dwelling is guarded by a ferocious mastiff. In the summer, these nomads move with their herds of yak to higher pastures and still live in their traditional tents. Not surprisingly, the interior of their one-roomed house is set up like a tent; a wood-burning mud stove at its centre, a small altar at one end, and sacks of tsampa and other foodstuffs and boxes of all their possessions neatly stacked along one wall. We are offered delicious bowls of a thick gruel made of tsampa, dried cheese, salted tea and butter. The men are wearing Mao suits but the women are traditionally dressed, their hair long and braided into tiny plaits. They stand around us, passing comments and laughing shyly. They refuse to believe that I am Tibetan and a part-Amdo at that!

The road follows the shoreline. We pass huge herds of yak and more depressingly, cultivated fields where nomads-turned-farmers, some in tractors, are harvesting barley. The agriculturalisation of traditional pasture is already in process and the nomads themselves are partly to blame. How long before Chinese and Muslim farmers with their superior experience and techniques take over the land and marginalise them?

We come to a hotel complex, its entrance guarded by a bizarre sculpture, a giant fist clutching a dorje, a crude attempt at ethnic sensitivity. Bits of the sculpture have already peeled off. Behind the hotel are scores of cottages designed to look like nomad tents. They are mostly half-built and already disintegrating. A lone Bactrian camel sits in the distance, waiting to give guests rides? The hotel itself seems empty, like a forlorn, out-of-season resort. As we prepare to leave, a Chinese TV crew enters the grounds and sets up a shot. A group of actors dressed like nomads in their Sunday best are made to walk towards the camera, the fisted dorje sculpture in the background. As they approach the camera one of the "nomads" peers through a pair of binoculars, theatrically waving it this way and that. I can imagine the commentary: Our nomadic brethren of the Qinghai plateau now enjoy the fruits of material progress, etc.

During our brief stay in Kumbum we have seen numerous television programmes that are obvious propaganda pieces aimed at fostering a sense of big-brotherly concern for China's minorities. In the rural setting of Kumbum, such old-style, state-sponsored programmes seem at odds with the more popular serials and music videos that everyone seems addicted to - stylishly made programmes that broadcast the alien but alluring lifestyles of China's new, urban, capitalist elite. The two seem irreconcilable and even an newcomer like me can see that the country is on the brink of a major crisis. What will happen to Tibet when these conflicting ideologies and economic contradictions finally spill out into the open?

We walk onto a jetty behind the hotel where a few fishing boats are moored. A large, newly-built stupa stands beside the shore, looking strangely out of place. In the distance, a mysterious wooden structure on stilts emerges out of the water like an abandoned pier. We later find out that this used to be a missile testing range. Two brand new Land Cruisers drive onto the jetty; a couple of Chinese military officers and their families out sight-seeing. They look at us curiously; we stare back at them. To them we must look like a couple of foreign tourists. To me, they are the aliens. We seem to be the only people about.

The overwhelming sensation is one of silence and space. The gentle sloshing of waves and the creaking of boats seem unnaturally magnified; the pure blue surface of the water stretches infinitely into the horizon. Behind us, the line of rounded mountains stands out in clear relief. The intensity of light has an hallucinogenic effect; we might be actors in a dream sequence from a Fellini film. A numinous calm pervades the place and lulls me into a reverie. So this is Tso Ngon! I'm finally here… I try and inject a sense of significance - the epiphanous thrill of self-discovery - into this moment that I have so often imagined, but all I can retrieve is a feeling of unreality and a sense of emptiness, buoyed by deeper unresolved emotions that once again question who I really am and what I hope to discover by coming here.