Here is a graphical comparison of many of the world's Subway systems at the same scale. This may be useful in the upcoming CIty Contests, or it may not be. However, here it is:http://fakeisthenewreal.org/subway/
Also, historical maps overlaid on their Google map images:http://howbigreally.com/dimension/cities_in_history/
if there's one thing I can't stand, it's a butterfingered walrus!