Subway system of Seoul, South Korea
Subway system of Berlin, Germany
A few weeks ago, I saw a link (via Treehugger) to a set of to-scale illustrated renderings of the subway systems from major cities around the world. Above, you can see the subways of Seoul and Berlin. On US-based artist and urban planner Neil Freeman's website, you can see dozens more.
For the record, Ottawa's proposed 3.2 km subway would look something like this (although perhaps not as straight) when placed on the same scale:
It looks kind of funny on this scale, doesn't it?