Humaling Tunnel successfully holed through

Workers work at the construction site of Humaling Tunnel, the last tunnel being constructed on a major railway connecting Lanzhou City in Gansu with the southwestern metropolis Chongqing, in northwest China's Gansu Province, June 19, 2017. After eight years of construction, the 13.61 km long Humaling tunnel was successfully holed through on Monday. (Xinhua/Guo Gang)