Kawah Ijen volcano, in East Java, Indonesia, is home to the largest acid crater lake on Earth. Photographer Olivier Grunewald and Vulcanologist Regis Etienne spend 30 nights here capturing a unique volcanic event - blue flames of burning molten sulfur. This "blue fire," as natives call it, can rise to 5 meters. This inspiring place was introduced to the world in the IMAX film "Ring of Fire."