Tsomgo Lake & Nathu La

Tsomgo, which means source of the lake in Bhutia, lies 40 kilometres east of Gangtok on the road the army keeps open to the Chinese border. It is an oval of glacial meltwater about a kilometre long at 3,753 metres, ringed by bare ridges that hold snow into May; Sikkimese Buddhists treat it as sacred, and lamas once read omens in the colour of its water. From December to February it freezes hard enough to walk on at the edges.

In spring primulas, irises and blue poppies come up around the shore, and the yaks that wait by the road wear red pom-poms and carpets for the photograph. Fourteen kilometres further the road tops out at Nathu La, 4,310 metres, a pass on the old wool-and-silk route to Lhasa that was shut after the 1962 war and reopened for border trade in 2006. Indian citizens with a permit can walk up to the fence, look at the Chinese post a few metres away and sign the book in the Indian bunker.

On the way back, Baba Harbhajan Singh Mandir near Kupup honours a soldier who died in 1968 and whom the men posted here still treat as on duty, keeping his uniform pressed. The gain from Gangtok is over two thousand metres in barely two hours, so the day is short, cold and thin on air, and best treated that way.