The 1914 Wonderground Underground Map, a mixture of cartoon, fantasy, and topological accuracy, by Macdonald Gill.
I love this map, and this article! Of course, one of the reasons I love the article (link below) is that it's about the London Underground, and it incorporates a lot of interesting historical background and contextual detail. Another reason is that it is written in a rather meandering way, going off on tangents that eventually lead back to the story at hand. Naturally, I admire this style of writing! And, most unusually, I have nothing more to add. Thanks, Andrew M., for sending the link to the map, which allows you to zoom around the map and see all the incredible detail. http://www.bbc.co.uk/news/magazine-25551751