North Sikkim — Gangtok, Lachen & Lachung

North from Bagdogra up the Teesta into Sikkim, about four and a half hours. Gangtok runs along a ridge at around 1,650 m. The afternoon is free, which matters more on this route than the others: the days that follow gain a great deal of altitude quickly, and starting rested is not a luxury. Permits for the north are processed while you are in town and need the identity documents brought with you.

East to Tsomgo at about 3,780 m on the old Silk Route road, with Baba Mandir beyond it. Besides being the region's best-known excursion this is useful preparation — a day spent near four thousand metres and a night back at sixteen hundred is close to the classic acclimatisation pattern, and the north Sikkim road goes considerably higher than this. Back to Gangtok for the night.

A long day north, following the Teesta through gorges that are among the deepest in Sikkim, past the Seven Sisters and Naga falls and through Chungthang where the river's two arms meet. Lachen at about 2,750 m is a small Lachenpa village that until recently was a summer settlement — the community still governs itself by the Dzumsa, its own traditional council. Accommodation here is simple by design; there is nothing else in the valley. Early night, because tomorrow starts before dawn.

Out before first light for Gurudongmar, above five thousand metres and one of the highest lakes in the world, held sacred by Buddhists, Sikhs and Hindus alike. The road is rough, the air is thin and the excursion is entirely conditional — army permission, snow and each traveller's own condition all decide it on the morning, and it is refused often. Back to Lachen for breakfast and then south and east to Lachung, another valley village at around 2,700 m, arriving in the afternoon.

Up the valley to Yumthang at about 3,560 m — the valley of flowers, where from late March into May the rhododendron and alpine species come out across the meadow and the hot spring sits across the river. In winter it is snow, which is its own reason to go. Zero Point beyond it is higher again and needs a further permit and its own vehicle. Then the long drive back down to Gangtok, which takes most of the afternoon and evening.

A deliberately gentle day after three hard ones. The Namgyal Institute of Tibetology holds one of the great collections of Tibetan manuscripts and thangkas outside Tibet and is closed on Sundays. Do-Drul Chorten of 1945 stands nearby inside its ring of prayer wheels. The afternoon takes Tashi and Ganesh Tok for the Kangchenjunga view, the handicrafts directorate, and time on MG Marg, which after Lachen feels like a metropolis.

The Teesta road back down to Bagdogra, about four and a half hours, retracing the first day in reverse and dropping out of the mountains into the tea and then the flat. An afternoon flight is the right choice: this road is subject to landslip in and after the monsoon and there is no quick alternative, so building in margin is simply sensible rather than pessimistic.