You do that the same way you add lines to the Bus system - by clicking on the Metro station icon and building a new one, or clicking over an existing station, which will trigger the line interface. To finish the first line, simply click again on the last station you've placed. The track can form bridges over bodies of water or ravines but the tunnel to bridge system does not have a very large amount of leeway and needs enough space. Unlike a tunnel, a metro line never needs to come to ground level, if you don't need it to! You can, however, change the depth slightly, as to prevent station placement, and then use the familiar point system for the necessary adjustments. The process is similar to building a tunnel (using points to change direction and height), and each click will attempt to place another station, unless there is an obstacle on the ground. When the player places his first station, he will automatically start tracing the track of the first metro line. Note that stations can only be placed at a certain depth - the metro track, however, can also go overground. He can then start placing metro stations - a 40x40m ground building that needs road access, and also has an underground part (so you can't run other tunnels right underneath).

To use the metro, the player must first place a Metro Company in the city.

The Metro system is similar in complexity to the Bus system.

Cities xl 2012 guide