our correspondent stephen mcdonell went to see how they will work. when athletes arrive in beijing from overseas, if their events are in the mountains, they'll be able to take a high—speed train there. that's because some of these trains are operating completely within the bubble. tannoy: ladies and gentlemen, welcome to take this train. - and soon, they'll find themselves racing along at 350kph. zooming through beijing's arid north and taking in the views. though freezing cold, this is an area of low winter precipitation, meaning that mountains of artificial snow will be needed for the coming olympics. well, this is taizicheng, one of the main stations for the winter olympics. it's cold up here. from today, this entire station is closed to the public. the bubble walls are coming up.