Some of London's tube stations are sprawling behemoths.
Picture the labyrinth beneath King's Cross, which connects six different tube lines, or the complex that joins Bank and Monument, which between them share three ticket halls.
If you can't visualise King's Cross, that's not a problem: TfL's release of the plans for all 124 tube stations situated below ground level means we can inspect their byzantine layouts directly.
Here, for example, is the official diagram of King's Cross:
It's a map that might well set your head spinning, and not only thanks to the axonometric projection chosen by TfL, which warps the perspective and makes the station look like something out of Inception.
Happily, not every tube station is such a rabbit warren of tunnels. Unsurprisingly, stations served only by a single line tend to be much smaller, and simpler to navigate.
Kilburn Park and Wanstead
Kilburn Park on the Bakerloo line is a model of simplicity: its single entrance hall connects directly to the platform level via two escalators.
Wanstead on the Central line is built to much the same design:
Wood Green, Bow Road and Temple
These aren't the most space-efficient arrangements, however. Wood Green on the Piccadilly line situates the ticket hall and escalators more centrally, so the entire station is only as long as the platforms:
This might be about as small as it's possible to make an underground station with escalators.
When the platforms are closer to street level, it's possible to build a shallower station, with short flights of stairs leading down to the platforms instead of escalators.
This happens a lot on the District line: Bow Road is an example of the design:
Temple, like Wood Green, saves a little more space by situating the ticket hall directly over the platforms, rather than off at one end:
While we're looking at District line stations, a special mention must go to Mile End.
Here again, the stairways and ticket hall are located over the platforms. The station is somewhat wider than the typical District line station — but that's because its double-sided platforms are also served by the Central line.
It's an impressive feat of architecture to squeeze four sets of rails into such a compact space.
Redbridge and Hatton Cross
Redbridge on the Central line manages to simplify things further by using a single stairway leading down to a central platform, with westbound and eastbound trains arriving on opposite sides:
Hatton Cross, towards the west end of the Piccadilly line, shares a similar design, but is made shorter overall by once more locating the ticket hall directly above the platforms:
What about the deep tube stations? Possibly the most compact of these is Chalk Farm on the Northern line.
The above-ground ticket hall is a small triangular vestibule with lifts and a spiral staircase leading directly downward to platform level. It's hard to get much neater than this.
Heathrow Terminal 4
The award for the most efficiently designed tube station has to go to Heathrow Terminal 4.
This station has just one platform and one set of rails, served by trains travelling in a loop from Hatton Cross round to Heathrow Terminals 1, 2, 3.
The station also doesn't have any escalators or stairs: passengers walk from the ticket hall directly onto the platform.
To be sure, it's a bit of a special case. You couldn't build a tube station like this in zone 1.
But let's think of it as a special treat for visitors flying into London — the gentlest possible introduction to the underground, before they travel into town and start having to puzzle their way through our maze of a travel network.
All diagrams © Transport for London