Mount Bromo is actually the youngest of five calderas, the first of which began to take shape more than 820,000 years ago. Since 1804, Mount Bromo has erupted more than 55 times, making it one of the most active volcanoes in Indonesia. The Ijen volcano complex is a group of composite volcanoes located on the border between Banyuwangi Regency and Bondowoso Regency of East Java, Indonesia. It is known for its blue fire, acidic crater lake, and labour-intensive sulfur mining.