Most people think exploring Kauai's roadless Napali (The Cliffs) coast means driving to the end of the road on the north shore and embarking on the 11-mile odyssey that is the Kalalau Valley Trail.
Not so. Some of the best hikes begin on the other side of the island, off the road that climbs alongside Waimea Canyon to Koke'e State Park.
From this mountainside direction, the cliffs radiate out in ridges, like spokes of a wheel, separated by valleys about 2,000 feet deep. All are reachable via 4WD roads/trails. One of the best, the Nualolo Cliff Trail, begins very near the state park visitors center, a 7.5-mile roundtrip trek through native subtropical birdlands that drops about 1,500 feet along the way---and reaches a red-cinder lookout that will curl your toes (though it's not inherently dangerous).
A connector trail links the Nualolo to its sister ridge, the Awa'awapuhi Trail, also spectac. (Ask locally before making this loop, since the connector trail sometimes gets thrashed by heavy rains.) See pages 163 and 168 in Kauai Trailblazer.