A cute comic by XKCD published the other day shows all the subway networks in North America falsely connected:
It was interesting to me how few there are on the whole continent; that map even includes Mexico and Canada!
For comparison, here is a subway map of just Tokyo:
And on top of that sits this network of JR trains (plus a whole bunch of private lines mostly not listed on either of these maps):
Makes the North American map look rather pitiful by comparison.