We are back to Heidelberger Platz where an U-Bahn train leaves the station. U-Bahn trains have always been yellow while S-Bahn trains are red (although they also have a touch of yellow). I really love this station, those vaulted ceilings and beautiful lamps make for such wonderful details. The walls of this station are also lined with photos of the city of Heidelberg which add a really nice touch.
Here is a look inside the one of the cars on line 3. These are the "older" type style of cars that were modeled on the original U-Bahn carriages. This is the only type of car that travels on line 3, but some of the more modern lines have the totally open carriages like you see on some line of the Paris metro and in Toronto.