The 656m-high still-active volcano of Gunung Api can be climbed for awesome views (especially at sunrise) in two to three hours if you are fit, but the unrelenting slope is arduous and the loose scree is dangerous on descent. Take lots of water and don't climb if it is wet. Guides (from 100,000Rp) are prepared to accompany hikers but the path up is fairly obvious. Your boatman will drop you at the start of the trail.