The London Tube Map is a genuine design classic, and while the actual service may have its ups and downs the map itself remains a constant of concise clear information able to be used by even the most inebriated traveller tracing their route with a grimy post kebab finger with their face no more than 3 inches away.
Designed by Harry Beck, a draughtsman working in the London transport office in 1931, it was initially rejected as being "too revolutionary" but it now has iconic status and attracts much reworking including re-labelling, 3d versions and Londonist favourite, Animals on the Underground.
All of these alternative versions as well as historical and future maps can be found in a frankly worryingly extensive list over at Mappers delight.
It even includes a link to a Way Out map for when you want to impress your visiting friends with a well timed, "No, we're getting out at East Putney, we want to get on the last carriage" comment.