JThe Ijen volcano complex is a group of composite volcanoes in the Banyuwangi Regency of East Java, Indonesia. .

It is inside a 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 (api being "fire"); Mount Merapi in central Java and Marapi in Sumatra have the same etymology.

Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones run east-west across the southern side of the caldera..

Blawan Waterfall is located in Kalianyar village, Sempol district. It is about 52 km of Bondowoso town. Blawan Waterfall is the continuation of Kali Pahit River, which is also the disposal place of the water from Kawah Ijen, which contains of much sulfur.

The water from Blawan Waterfall goes down to the earth then it shows up again in Asembagus, Situbondo district.

Blawan waterfall is surrounded by sharp cliffs and there is also stalagmite cave. It is believed that a long time ago this cave was often used for meditate.