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The Qinghai–Tibet railway is a high-altitude railway that connects the Chinese cities of Xining and Lhasa. Completed in 2006, it is the world's highest railway, with an average elevation of over 4,500 meters (14,800 ft) above sea level. The railway spans a distance of approximately 1,956 kilometers (1,215 mi) and passes through some of the most challenging terrain on Earth, including the Tibetan Plateau and the Kunlun Mountains.