I'm seriously thinking about trying a walk from one station to another along one of the train lines, but haven't worked out where I should aim for. Some of the gaps are Quite Large (there appears to be one that is 30km, based on this page), and I'm not sure whether there are bike/pedestrian paths between all of them. Possibly will go for one of the older lines, where the stations are quite close together, and see what I can see in terms of pretty buildings.