Taihang Tunnel, located in Taihang Mountains in China, is the fifth longest railway tunnel in the world. The 27.8km long twin tube tunnel was built as part of Shijiazhuang Taiyuan railway project to cross the Taihang Mountains. Construction of the tunnel was completed in December 2007. The tunnel passes through Yue Xiao, the main ridge of Taihang Mountains, with a maximum cover of 445m. The left track has a length of 27,839m, while the right track is 27,848m long. The distance between the two tubes is 35m. The tunnel was designed by Poyry.