Ijen Crater, Indonesia (4/20)

Ijen Crater is famous for its stunning blue flames that can be seen at night, caused by the combustion of sulfuric gases. Located on the island of Java, the crater offers a challenging hike to its summit, where you can witness the incredible blue flames and take in panoramic views of the surrounding landscape. The turquoise crater lake, one of the world’s largest acidic lakes, is another mesmerizing feature of this volcanic site.