Not usually seen as a white-knuckle activity, travelling by train has just got rather more adventurous.

Completed last year, the Golmud to Lhasa line in Tibet is the world's highest (17,000ft, for the detail-obsessed) and is the only train in the world where oxygen is pumped into the carriages.

You may want to ponder this as you trundle over the permafrost: will this new train line destroy one of our last wildernesses or - as the Chinese government claims - alleviate poverty by bringing in tourists and lowering freight costs for the Tibetan people?

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