The drive along this stretch of Highway 19 can be very long and boring. Don't let that frustrate you or cause you to lull yourself into missing what sights there are along your journey. Going north away from Hilo, there are several places to pull off to see beautiful waterfalls. Be sure to take the side-road trip up to Akaka Falls. The turnoff is between mile markers 13 and 14.
This state park is beautiful and offers two hikes that are fairly easy. The large waterfall here plummets a whopping 420 feet. The walk is very beautiful, through a very thick forest of bamboo and other rainforest-type vegetation. Be sure to take advantage of the decent restrooms here (not porta-potties), as you won't see another public restroom for what will seem like an eternity!
After you leave this park, continue north on Highway 19. At about the 16 mile marker, you will cross over a large gorge that has two nice waterfalls. You will be able to pull off safely to park your car and get out. The water from Akaka Falls flow down here and empties into the Hakalau Bay beneath you. The views are spectacular!