Well, becase the whole story is based on my findings of the symmetrical structure of London, no wonder I'd put up part of London map as its cover. Sorry I don't know how to rotate the image properly, so please lean to your left if you want to have a good look at of it, London Face.

Nose, Waterloo Bridge and Elephant & Castle

Left Eye, Leaden Hall Market

Right Eye, Westminster Cathedral

Brain, British Museum

The reason of such symmetry in London's city structure is explained in Chapter 10(I made a mistake when I said it was in Chapter 101 before, sorry. What Sherlock didn't mention there is that actually London city and London Bridge is right where first Roman army landed on this land, thousands of years ago, all because its ideal slope of river bed shaped by the turn of Thames. Of course that's only my deduction of what I know. Welcome to share your idea with me

Also, I think it would be a spoiler if I put this explanation that the beginning of the story, so thank you for seeing this at the end

Best!