The descent into Wapio Valley on the northern green nub of the Big Island of Hawaii really is a trip back in time, with little having changed since Kamehameha the Great surfed here as a boy and the Polynesian voyagers tended taro fields. The country blacktop that is Highway 240 ends at Waipio Lookout, where a comically steep concrete one-laner (4WD only!) hugs a mossy cliff face to the streamside bottomland. It's a 20 minute walk, down about 500 feet.
Most visitors head to the rough beach to watch surfers ride Kamehameha's waves. Adventure seekers boulder-hop right at the beach to look up at Kaluahine Falls or go left to make a stream crossing and head up the switchbacks of Muliwai Trail into the wooly wilderness. A few people (some in rented Jeeps or on horse-drawn tours) go left, up Waipio Valley, making a stream crossing through a jungle, passing fishponds, more falls, and a few laconic wild horses.
But very few tourists find the "back door" to the valley, since you need to take a leap of faith at a second stream crossing by walking up the "stream," which becomes a road after a few hundred feet. This path is the time travel. Sure, stick-frame shacks have replaced woven hau huts, but the taro fields date from antiquity, in many cases tended by the same families. The road hugs one side of the valley in a tropical arboretum and the view across the fields is of Wapio's steep walls laced with strands of falling water. The whole escapade takes but a few hours, but by the time you make it back up to the lookout the mental time will seem like a century.