Chengdu-Kunming Railway (1970)
One of southwest China's first great rail engineering feats, the 1,100-kilometer line took a decade to build through Sichuan and Yunnan's mountains and rivers in the 1960s, largely by hand.
Its completion in 1970 finally linked the southwest interior to Kunming and opened the region economically.
It set the pattern for southwest rail: tunnels and bridges dominate, and projects often run 80% underground or elevated.
The Huang-Bai line shares that pattern, with more than 80% of its route in tunnels and bridges, which is why each breakthrough is a major milestone.
