(All pics 23.6.2015 copyright Steve Sainsbury/Rail Thing)
I always assumed the closest thing to rail heaven (if your interest extends to trams and narrow gauge!) would be somewhere in Switzerland, perhaps Aigle or Interlaken Ost, or possibly Wales (Porthmadog or Llanberis) but I think I've found it in Italy of all places!!
Porta Maggiore is a stop on four of the city's tram routes, but also on the 950mm suburban line to Giardinetti and with the busy main line into Roma Termini as a backdrop. The whole area is intersected by a number of Roman aqueducts and the trams and trains happily thread through the arches. The whole area is so busy that there seems to always be at least one thing moving, often more!The narrow gauge line seems to have a constant procession of yellow and white trains intersecting the whole site, cutting across tram tracks, through arches, past what appears to be a Roman temple and then across one of the busiest Rome streets (all completely unprotected of course!) and down a side street into the city centre.
Later in the week we went on a tram tour from here and in the evening the place is even better, busier and with nicer light. Well worth a visit even if trams and light railways aren't your thing!