With an angel to the gates of hell

After labouring our way up to the 16,000ft Kamba-la pass in a Land Cruiser, above the great Yarlung river and beneath the brown hills of high Tibet, we finally reached the crest. There below us on the other side were the gorgeous turquoise waters of the sacred Yamdrok-tso Lake, pure snowy peaks looming behind.

We were on one of the world's great journeys, travelling the Friendship Highway for 600 miles between Lhasa in Tibet and Kathmandu in Nepal. Until it drops off the Tibetan Plateau, the road is never less than 12,000ft high and it threads along fertile valleys between beautifully barren hills, with the grand Himalayas appearing on the skyline.

In our Land Cruiser it took only a week to travel the highway and we became firm friends with our Tibetan guide, Wang Dac, a small, spare man of 32 who looked nearer 50, and our driver, Tashi, who possessed a cherubic face and the driving skills of an angel.

Our first day took us down the beautiful Lhasa valley, past sunlit autumnal trees and the fast-flowing river, before climbing to Yamdrok-tso. Yamdrok-tso is both sacred and "dead", in that there are no significant rivers flowing into or out of it. A controversial hydroelectric scheme is now using the lake to generate power for the Lhasa area but while the authorities claim that power from the project will be used to pump water back up from the Yarlung river, the wonderful skipping stones show that the lake's level has clearly fallen and, anyway, the muddy river water would change the superb colour of the lake.

Leaving Yamdrok-tso, we arrived in the ancient town of Gyantse in the late afternoon. Today it is still dominated by the great dzong, or fort, that the Younghusband expedition of 1903-1904 had to take by storm when it threatened their communications with India. Beneath the dzong lies one of Tibet's greatest glories, the Kumbun, a stupa of six symmetrical, but reducing, floors, topped by a golden dome. Its 70-plus chapels contain beautiful wall paintings, for some reason left intact by the Red Guards who destroyed most of Tibet's religious heritage.

The fields immediately outside the town were full of peasants threshing their harvest. Dust caught in the golden afternoon light and the farmers sang as they tossed their crop into the breeze or drove teams of cattle and horses over the stalks.

Half a day's drive further brought us to Shigatse, whose 80,000 people make up Tibet's second city. At its heart lies the great Tashilunpho Monastery - seat of the Panchen Lama, who is Tibet's second most senior cleric, and once home to thousands of monks. As we admired the lusciously decorated tombs of the Panchen Lamas a group of young monks grabbed my guidebook and insisted on having every picture explained before releasing it.

Wang Duc told us that the large pack of well-fed dogs lounging in the monastery's sunny corners were reincarnations of inadequate monks. We weren't sure if he was joking. Leaving the monastery, we passed brightly clad pilgrims muttering mantras and spinning the large brass prayer wheels.

Back on the Friendship Highway, a side valley brought us to the great Sakya Monastery. The seat of the Sakyapa school of Tibetan Buddhism was founded in the 11th century and it is surrounded by huge fortress walls and watchtowers. Its quadrangles are reminiscent of an Oxford College, the crimson robed monks gossiping in the sun like students anywhere. Shafts of sunlight penetrated the dark chapels and halls, illuminating their blood red cushions, elaborate hangings and smiling Buddhas.

A long, hard road took us to Rongphu, at 17,000 feet the world's highest monastery. A small community of monks and nuns, along with a herd of Yaks, eke out a living in this environment of rock and ice. We sat in the lee of the monastery wall and stared at Everest, magnificent at the far end of the valley.

Another five miles up the valley brought us to Base Camp where flimsy-looking tents nested on a rare patch of grass, sheltered by a moraine. Here, we ate a delicious supper of honey pancakes and fried rice and that night I slept in five layers of clothes.

The next day we spent a long 10 hours on the road getting to Zhangmu on the Nepalese border. Crossing wide, desolate plains flanked by stark, brilliantly hued hills had brought us to two high passes over the Himalayas and surrealistically wide, rolling pastureland amid huge, snowy peaks dimly appearing among the clouds.

Dropping down from Nyalam (the "gates of hell") into a stupendous gorge, the vegetation gradually became greener as we lost height and the land saw more rainfall. In places, rainy season landslides had narrowed the road to a single, tilted track and, with no barriers, we could see the river at a sickening distance below us: one skid would have done for us.

It was a relief to reach Zhangmu. Our final day's driving was to be with a callow youth in a bald-tyred banger rather than Tashi and the Land Cruiser. We made it all the same to the chaos of Kathmandu and our first beers of the week.

William Mackesy travelled with Global Expeditions of Chengdu, China (tel: 00 86 28 557 2936, fax: 00 86 28 557 0457). Starting from the UK, Steppes East (01285 810267, www.steppeseast.co.uk) runs similar 16-day Roof of the World tours from £2,770 per person, fully inclusive