On our very last day on Maui (and in Hawaii, in general), we drove to the top of Haleakala Volcano. In the Hawaiian language Haleakala means "the house of the sun". The volcano is 10'023 ft (3055m) tall and it is "potentially" still active.
It is a quite interesting experience to drive to its top from the sea level: at first you are below the cloud cover, then you are driving through the clouds, and in the end you find yourself above them. I do not know of many places on earth that you can experience something as magical as this and I would strongly recommend finding time to get to the top of the volcano if you are ever on Maui.