It is mostly famous for two reasons. First, it is the home of the most acidic lake in the world. Sitting in the middle of the volcano, this amazing turquoise-colored lake is loved by anyone that sees it and is probably one of the most photogenic lakes in the world. Secondly, there is the phenomenon known as the `Ijen Blue Fire`. This phenomenon occurs around the clock, but can only be seen by the naked eye in the dark of night.