Kukui Trail
The trail that actually goes down into Waimea Canyon.
A 2,000-foot drop off the west rim to the river at Wiliwili Camp, and the climb back out is the whole price of admission. Go at dawn and carry more water than feels reasonable. The Iliau Nature Loop at the same trailhead hands over the canyon view for free. Find it along Highway 550 past the 8-mile marker.