The Transport for London tube map, building on Harry Beck's pioneering work in 1931, is rightly hailed as a masterpiece of simplification and clarity in data visualisation.
But it's only when the familiar map is compared with this map, showing the actual geographic relationships of stations and the layout of TfL's tracking, that you really begin to understand what a fantastic, gnarly, organic hairball the tube system actually is. It's also a great source of plot devices, showing all the different places that trains can be diverted to — Speed 5: London Edition?
This map of London's tube shows disused stations, track layout and more
[Jonn Elledge/City Metric]