Ijen

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.

It is inside an eponymous larger caldera Ijen, which is about 20 kilometres wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name "Gunung Merapi" means 'mountain of fire' in the Indonesian language; Mount Merapi in central Java and Marapi in Sumatra have the same etymology.

Ijen Geopark stretches across the entire regency which is specifically in the Mount Ijen area, Pulau Merah Beach, and Alas Purwo National Park. It has various geological, biological, and cultural sites.

Source: Wikipedia