Crisp and clean but very thin air!

So now we are in Leh, in the Ladakh region of Northern India, 3500m up in the Himalayas. Beautiful blue skies but cold nights. Leh sits in a basin surrounded by dramatic mountains; many snow-capped.
The season ended here about a month ago, so it is quite quiet and empty of tourists with restaurants and guest houses shutting down for winter every day.
We walked up the mountain to the north of the town today to the old palace and then even higher up to a monastery that used to be the highest building in the world until a couple of decades ago. Thousands of prayer flags stretch out hundreds of yards between peaks as you look down on the entire town of Leh. We sat at the top eating cold samosas appreciating our lot that we were not stuck in an office or face down in a stranger's grotty bath tub!
Tomorrow we set off on a wee two day trek with a somewhat basic map, summer-weight sleeping bags and no guide......