The railway was build as a fast way to travel around the map. It was commissioned by NemesiS_ITA and MarshallTV to a mysterious builder.
On the dynmap the railway is shown by the yellow line. When you zoom in on the railway you can see green stations, in addition to the 4 main stations that are marked on the map these are the places you can acces the railway. Do not make towers to acces the railway! The stations aren't that far apart.