It isn't very famous, but I like the opening line of Mortal Engines:
It was a dark, blustery afternoon in spring, and the city of London was chasing a small mining town across the dried-out bed of the old North Sea.
It just throws you right into this weird post-apocalypse where cities run around on wheels eating each other. Honestly I think Mortal Engines has some really cool worldbuilding in general.