Taking two cable cars to the top of the Aiguille du Midi (3800 m high) and later the rack and pinion train to the Mer de Glace glacier was a mind blowing experience. We were lucky to get excellent visibility. Advice for the unwary - the Aiguille du Midi rail lifts ascend about 2500 m in about half an hour. This is hazardous for anyone with heart or lung problems or is petrified of heights!