London? London has 13 major railroad stations and they're all dead ends.[1] Crossrail, with expensive tunnels, now provides some east-west through services.
There's a fan-out at London Bridge to three more stations, but everything dead-ends within 2km or so. You can't continue west or north and get out of London on any of those tracks.
No, trains through London Bridge and Blackfriars continue North via a tunnel through City Thameslink, Farringdon, St Pancras and join the Midland Main Line or East Coast Mainline.
Yeah the only through-running trains through the actual city centre are the Elizabeth line and Thameslink. If you count slightly outside the city centre, you could also consider the West London Line (southern and overground), and the other overground from Croydon to Islington to be throu-running. But they slightly miss the city centre.
> Terminating a train and turning it around takes a lot of space, space that is usually unavailable in a city center.
This doesn't happen in London in my experience. Trains don't turn around, instead every train is double-ended. The driver gets out of the cab at the terminus, walks to the other end of the train and gets in the other cab. They can do it faster than the passengers disembark.
That's what turning around a train means. The point is that a train at a terminal station is "occupying" a disproportionately long section of track, and as a result you need a multi-tracking and a ridiculous number of platforms to allow storage of trains to handle enough trains... while a through-running station can achieve the same capacity with just two tracks and 2-4 platforms.
Huh, I never thought of that as the reason for the small number of long-distance platforms in, for example, Berlin Hauptbahnhof (all through-running) compared to some other big-city stations that are terminal.
There are several solutions to turning around at a terminal. Sometimes there's a turnaround loop. Grand Central has two, one on each level. Older systems would detach the engine, rotate it on a turntable, and reattach it at the other end of the train. Double-ended trains are far more common today, since control from either end was solved long ago.
[1] https://en.m.wikipedia.org/wiki/File:Major_railway_stations_...