The Stadtbahn is the main overground east-west railway in the city of Berlin, Germany. This entirely elevated, four track route carries an interesting array of S-Bahn (the Berlin metro), regional and express passenger trains (from Germany and further afield) through the city centre.
By JuergenG – Own work, CC BY-SA 3.0, Wikimedia Commons
The interesting architecture and variety of trains that use the line would make for some very interesting modules.