The subway system of Paris, France is quite developed, with 16 separate lines (3 of them now automated), 320 stops, and a total of 245 kilometers of track. Having lived in this city my entire life, I would be especially enthused to see the following lines modeled. L10's route features some of the eldest pieces of track from the early days. It features an unusual section between stations Cardinal Lemoine and Maubert Mutualité: trains there can be routed off the normal route and sent to a maintenance access tunnel; what's unusual is how this access track lays under the normal route's track, which separate at one point to form an opening to this 2nd-level underground (Shown in this video at 5'00) But its most amazing part is the western portion, around Porte d'Auteuil, Michel-Ange Molitor, deprecated station Porte Molitor and the Atelier d'Auteuil maintenance yard. This area is a delightful mess of multiple tracks running in all directions, switches, and legacy access tunnels from the early days of the subway system (shown on this video @21'15). L10 also features the disassociated half-stations Eglise d'Auteuil and Mirabeau with its prominent elevation ramp (shown in this video). L2 and L6 both have an interesting loop-shaped terminus at Nation. Both loops are interconnected and give access to one of the oldest maintenance yards about 800 meters out, the Atelier de Charonne. Both also feature underground and overground parts; L6 crosses the Seine twice with great landscapes around those areas (the Eiffel tower, the national library...) L6 also features interesting maintenance-access tunnels near the Place d'Italie station: access to another historical maintenance yard, as well as a connection to the L7 route through a narrow tunnel where the track type changes from rubber-tyred-enabled to normal standard gauge only. Shown on this video (starting at 13'55) There is also something to be said for L8, with its long stretches of prolonged tracks outside of Paris on its eastern end, and for the 2-level of superimposed tracks shared with L9 between the Grands Boulevards and Republique stations, where one can sometimes see L9 trains when riding on L8.The rolling stock on this line has one of the most distinct, noisiest wheel screeching sound. It also has one of the few "ghost stations." (Stations that were closed during WW2 and abandoned afterwards in favor of a more ambitious new development plan.) All in all, the Paris subway system is a single system of finely interwoven tracks, with its maintenance vehicles roaming all around it every night, its set of abandoned tunnels, and its hidden depots where legacy rolling stock are said to be stored. There was a Microsoft Train Simulator user-contributed map that featured most of its tracks and stations, with which I had some fun in the early 2000s. Of course something so big is outside the scope of normal TSW routes, but I would be willing to pay more than the usual DLC price for something that would approach it, such as two lines made into one route, or some sort of modular route which might be expanded with more track being layed in multiple stages... The track layout illustrations are taken from the amazingly great CartoMetro website. Vising that link will provide you with a full picture of all the track layout and passenger route lines.
Adding these videos for L6 that showcase how beautiful it can get: Complete cab ride westbound: At 28'40, things get amazing between stations Bir-Hakeim and Passy with the train crossing over the Seine, then running overground between two Haussmann-style apartment buildings. As if it weren't enough, the Eiffel Tower is visible on the right during that crossing: Here's another well-shot cabride, this time inside an eastbound train:
