Workers lay tracks on the Dunhuang-Golmud Railway in Jiuquan City, Northwest China's Gansu Province, June 15, 2019. The last pair of 500-meter-long track were laid on the Dunhuang-Golmud Railway on Saturday, marking the completion of the track-laying work for the railway, which links Dunhuang in Northwest China's Gansu Province and Golmud, a city in Northwest China's Qinghai Province. (Photo: Xinhua)

Workers prepare to lay tracks on the Dunhuang-Golmud Railway in Jiuquan City, Northwest China's Gansu Province, June 15, 2019. The last pair of 500-meter-long track were laid on the Dunhuang-Golmud Railway on Saturday, marking the completion of the track-laying work for the railway, which links Dunhuang in Northwest China's Gansu Province and Golmud, a city in Northwest China's Qinghai Province. (Photo: Xinhua)

A worker lays track on the Dunhuang-Golmud Railway in Jiuquan City, Northwest China's Gansu Province, June 15, 2019. The last pair of 500-meter-long track were laid on the Dunhuang-Golmud Railway on Saturday, marking the completion of the track-laying work for the railway, which links Dunhuang in Northwest China's Gansu Province and Golmud, a city in Northwest China's Qinghai Province. (Photo: Xinhua)

Workers lay tracks on the Dunhuang-Golmud Railway in Jiuquan City, Northwest China's Gansu Province, June 15, 2019. The last pair of 500-meter-long track were laid on the Dunhuang-Golmud Railway on Saturday, marking the completion of the track-laying work for the railway, which links Dunhuang in Northwest China's Gansu Province and Golmud, a city in Northwest China's Qinghai Province. (Photo: Xinhua)

Workers lay tracks on the Dunhuang-Golmud Railway in Jiuquan City, Northwest China's Gansu Province, June 15, 2019. The last pair of 500-meter-long track were laid on the Dunhuang-Golmud Railway on Saturday, marking the completion of the track-laying work for the railway, which links Dunhuang in Northwest China's Gansu Province and Golmud, a city in Northwest China's Qinghai Province. (Photo: Xinhua)

Workers lay tracks on the Dunhuang-Golmud Railway in Jiuquan City, Northwest China's Gansu Province, June 15, 2019. The last pair of 500-meter-long track were laid on the Dunhuang-Golmud Railway on Saturday, marking the completion of the track-laying work for the railway, which links Dunhuang in Northwest China's Gansu Province and Golmud, a city in Northwest China's Qinghai Province. (Photo: Xinhua)