The intricate patterns of rail yards.
Subway riders never get to see the part of the network where trains pass the night, the rail yards where all the cars go when the system winds down, or when they need repairs. These spots – called "depots" in the London Underground – don't appear on traditional transit maps. But you can find them, if you're looking in the right places, on Google Earth. And they look like labyrinthine networks as intricate as whole subway maps themselves.
The spaghetti pile to the right here is the Beckton Depot on the east side of London at the end of the DLR line:
And here it is again, zoomed in, in a Google Earth view:
And she's repeated the painstaking process with all 17 depots in the Tube, most of them located at the end of lines and traceable through Google Maps and other online sources. She's turned all of them into postcards that transit geeks might use to commemorate the London Underground's 150th anniversary this year. "They're diagrams," she tells us by email "of parts of the Underground network which the average Londoner probably never thinks about – they're not accessible to the public and passengers can't travel to the depots – unless they've fallen asleep and nobody notices them!"
These are also the least glamorous parts of the London Underground (not to mention parts of it that are entirely above ground), which makes their translation into graphic design all the more charming.
Hat tip to the Transit Maps Tumbler.