The 2 southbound branches of the Northern Line leaving Camden pass really close together as well, quite amusing to be able to see right into another train while in a deep tunnel!
Even more dramatic, I find, is when you get a northbound from the Charing Cross branch going in the Highgate direction, entering the station simultaneously with a northbound from the Bank branch heading to Edgware, The original northbound route for the Charing Cross branch had almost a straight run into the Edgware platform, with a fork off to the right shortly before the station, to head to the northbound Highgate platform. But after the link up with the City branch, only the "right turn" there is used by the ChX branch (its Edgware trains diverging well before the station and arriving at the station from a different angle). But the fork
is now used to access both northbound platforms by Bank trains - they merge from the left as you get to the fork, with the option of going what is for them straight ahead for the Highgate branch, or swerving to the left to pick up the Edgware platform.
This means that in the scenario given above, the two train routes are converging as they meet in what was a tunnel junction but is now an X-shaped tunnel intersection, and both trains take quite a sharp turn as they almost meet and swerve away from each other, running parallel for moments, going at a fair speed, seemingly only inches apart. If you're on the left-hand side of a ChX-Highgate train as it gets to that intersection, and you're
not seeming to almost collide with a Bank-Edgware at the time, you can see the Edgware platform dead ahead as your train lurches to the right.
The reason I said this is
more dramatic than the similar southbound scenario mentioned is that (a) the speed at the intersection seems higher northbound, and (b) going north the trains on
both routes swerve away from one another, whilst on the southbound, one of them keeps fairly straight on (as I remember).
NB - anyone interested in this who looks for any old (or new) "cut-away" or 3-D drawings of these intersecting and interweaving tunnels will find a basic error in many of them (including in the case of a classic one from the 1920s which is frequently reprinted). They often have the labelling of the routes south of the intersections to and from the ChX branch and to and from the Bank Branch the wrong way round, the latter obviously (well, it's obvious with a only a moment's thought) being the ones on the
west side south of Camden Town. This mislabelling is self-evident from what you experience in the tunnels themselves, if you actually use trains running through there. But I guess such diagrams are often produced by people who don't use those trains, and/or by people with no sense of direction or spatial awareness - perhaps they're the sort who, if they use proper maps at all, turn them upside down if they're facing south...