One of the most otherworldly places in Indonesia, Mount Ijen is worth the trip to East Java. Though it can be quite a process to get there, should you go the adventurous route of using local boats! 

A crater of perfectly turquoise water is surrounded by volcanoes at this ethereal site. Hike up for the sunrise, rainbows, and gorgeous views into the crater below. Also check out the famous blue flame, but be sure to wear a gas mask as it’s quite dangerous to inhale the fumes.