永定河
The Fengsha railway runs up the Yongding River Valley from Fengtai District in southwest Beijing through the Taihang Mountains and across the Guanting Reservoir to Shacheng, on the Beijing–Baotou railway. The line crosses the Yongding River eight times through rugged terrain and has 67 tunnels and 81 bridges in all. The shortest tunnel, No. 056, just in length, is the shortest standard gauge rail tunnel in China.