When you fold the notebook length-wise (when the spine practically touches the long edge of the back cover), the fore-edge of the pages fan out. Only when the notebook is folded this way, does a subway map clearly appear. This is due to the fact that the map is printed on the edge while the notebook is positioned like this. You can hide the fact that you are consulting a subway map and be spared the embarrassment and scorn from locals.
The Fore-edge Subway Map appeared in the My Moleskine 2.0 Exhibition.