10 miles past the city of Hana is the Coastal part (Kipahulu area) of Haleakala NP. We did not get a chance to explore it well, mostly because it seems that for my parents traveling is not about travel, but about destination... So we just had enough time to walk to the Oheo Gulch (the Seven Sacred Pools) that you can see at the photo below:
I would definitely recommend spending more time there than we did. The whole places was very green and beautiful, and virtually tourist-free! And according to my "Hiking in Hawaii" travel guide, there are a few of Hawaii's most spectacular hiking trails there.