Waimea Canyon
Waimea Canyon was called "the Grand Canyon of the Pacific" by Mark Twain, and it's truly spectacular. While not as big as the Grand Canyon, it's still very large and has an interesting mix of rock and dirt canyon, rivers and jungle vegetation. At the topmost point you can drive to the elevation is nearly 4000 feet, and it drops off into the spectacular Na Pali Coast along the west side of Kauai.