Siegstrecke
The route runs on the Cologne–Aachen line (opened by the Rhenish Railway Company between Cologne and Horrem in three stages between 1839 and 1841), the East Rhine Railway (opened to Troisdorf by the Rhenish Railway in 1870, with an extension to Cologne opened in 1874), the Cologne Airport loop (opened in 2004) and the Sieg Railway (opened by the Cologne-Minden Railway Company between 1859 and 1862).