The quickest way the Pevensies know to get to Aslan's How (formerly the Stone Table) is to cross a river called the Rush. When they finally find it, after 1,000 years in Narnia Time, the peaceful little river that used to be no trouble to ford is now at the bottom of a deep gorge.
Susan: See, over time, water erodes the Earth's soil, carving deep into the...
Peter: Oh, shut up.
One of the funniest lines from the book that made it into the movie:
Peter: Girls can't carry a map in their heads.
Lucy: That's because our heads actually have something in them.