By some counts, Shanghai is the largest city in the world. (And, by all counts, it is definitely huge.) Evidence of this can be found in the complexity of the public transportation system. I love living in a city that has such great options for mass transit and enjoy the challenge of trying to navigate it all.
This is the latest metro map. Because of the upcoming World Expo, the system is being expanded in big ways. Since we moved here in August, at least three new lines have been added and many of the others have been extended. We live near Lines 1 and 3 (in the southwestern corner of the city) and can get to any stop on this map for approximately fifty cents. Awesome.