Blue no longer stands for cool here. The Ijen Volcano, famous for its blue lava, is another of nature’s marvels. Located in East Java, Indonesia, it is a group of composite volcanoes. The bright blue color is the result of sulfuric gases burning at a very high temperature of above 360°C. As these gases come into contact with the oxygen present in the air, they turn blue.

Alongside Ijen is the world’s largest sulfuric acid crater lake, which was formed by the blue lava. Its glory is best seen at night.