Ijen

Mount Ijen (Kawah Ijen) is an active volcano in East Java renowned for its luminous, highly acidic turquoise crater lake and rare electric-blue sulfur flames. Hikers typically embark on steep, late-night treks requiring protective gas masks to witness the combusting sulfuric gases inside the crater. As dawn breaks, the dramatic volcanic landscape is revealed alongside the world's largest acidic crater lake.

Commenters consistently express awe and fascination toward Ijen's otherworldly landscapes, frequently comparing the blue flames and turquoise waters to fantasy realms. While many are eager to add the hike to their bucket lists, discussions often center on the physical difficulty of the trail, the absolute necessity of safety gear against toxic fumes, and reports of increasing trail crowds.