Ijen Crater (Blue Fire), East Java

#summervacay Ijen Crater was one of the most intense and fascinating experiences of my trip. We started the hike at midnight to see the famous blue flames—caused by ignited sulfuric gas—which were otherworldly. After that, we stayed for sunrise, revealing a turquoise acidic lake inside the crater surrounded by rocky cliffs. The sulfur miners working inside the volcano are tough and inspiring. This isn’t an easy trek, but the payoff is absolutely worth the effort.