Traveler Donny Nugraha Pratama has captured stunning blue flames spewing out of the ljen volcano and illuminating the night sky in Kawah, Indonesia. /VCG Photo

Tourists had to travel for two hours to catch a glimpse of the nearly five-meter-high flames. /VCG Photo

The blue flames are not actually lava. The blue glow comes from high levels of sulphuric gas in the volcano. When the gas is exposed to oxygen in the air and burned by the lava, it emits a blue light. /VCG Photo

Kawah's Ijen volcano is one of a handful in the world where blue lights could be spotted. Other similar volcanoes are located in Iceland. /VCG Photo