Think very tall trees of all kind -- bamboo, palms, tulip trees -- lots of plants and foliage including a variety of ginger and way down below the road is the ocean.
The road is a narrow, winding road with a couple of one-lane bridges over waterfalls and streams and lots of cars pulled sort-of off the road to take pictures or just enjoy the scenery. It's almost always green and jungly (if that's a word)
And then the road opens up and you are back on Hwy 19 and almost in Hilo. You can also take it in the opposite direction and get a different perspective. At one end of the drive is a small restaurant selling fresh fruit smoothies, sandwiches, salads and baked goods. They grow a lot of the fruit right there and all the tables are outside on the covered lanai. Nice if you need a break.