No disrespect to the rim views of the Grand Canyon, but the only way to truly experience this wonder of the natural world is to float through it. For the last six million years, the Colorado River has been at work eroding the canyon into its current superb existence and, by extension, creating one of the most epic whitewater routes anywhere. Grand Canyon rapids predate the modern Class VI rating scale, so this is one of the few places in the world where, technically, you can see Class 10 whitewater. Crystal and Lava Falls, two of the most aggressive on the Colorado, can be rated as such depending on water conditions. But regardless of when you go and what section you raft, you’ll be treated to rushes worthy of the best amusement parks, and views you can see in Arizona and nowhere else.