A supposedly-dormant volcano, which had been last observed a bit too many years ago to be truly confident about. The natives called it Hongman, after a Chinese term for "To Deceive" (哄瞒), which many say sounds suspiciously like "hung man," alluding to death.
The sides are steep in mountainous formation, and can be seen from all angles of the island. It never, or at least, very rarely ever smokes from its top, and no one is able to get close enough to it to study it properly, due to violent reactions from the natives (they have the tendency to throw fire at anyone or anything that tries--including helicopters).
Anyone is welcome to make the attempt, however, and report back with any information. Just be sure to bring something fire-resistant.