Have you ever been to Tibet? Tibet is the largeest and highest area in the world. Its average altitude is above 4000 metres. It has the name of ridge of the world. The highest mountain Everest locates here. Most Tibetan beleive Lamaism which formes their own culture system. Therefore lots of people travel Tibet each year.
It's only possible to arrive Tibet by plane before. But from last year, Qinghai-Tibet Railway opened to traffic. It only takes 48 hours from Bei Jing to Lhasa, the capital of Tibet. Buidling railway in the area with an average altitude of above 4000 meters is the first time for China. There is no precedent in the world. There were hundreds of thousands of road workers worked hard for 5 years on the Tibetan Plateau. Now the Qinghai-Tibet railway is the highest railway in the world. I travelled Tibet by plane last time. I decide to travel it by train next time.