DAY SIX: Continue northwest on Route 19 to rugged, isolated Waipio Valley, on the windward side of Kohala Mountain, for incredible vistas and a return to a verdant, prehistoric Hawaiiyou'll need a four-wheel-drive vehicle to access the 2,000-foot vertical cliffs, waterfalls, and mile-long gray-black beach. The trip is a thriller: The one-lane road down to the "Valley of the Kings" has a 33 percent grade in some places (you'll make the whopping 1,000-foot descent in less than a mile). Or Naalapa Stables lets you explore the area like a paniolo, or cowboyon horseback. The Waipio River, rainforest, and taro fields cover the valley, also home to the Big Island's tallest waterfall: the earth-shaking, 1,300-foot Hiilawe Falls. Then, if you can bear to tear yourself away from all this beauty, take your wheels down Route 19 to the Kona airport and fly back to reality.