Ijen Crater is a crater lake located on the top of Mt. Ijen in the Ijen Tourism Park Nature Reserve, Bondowoso Regency and Banyuwangi Regency, East Java province. This lake is about 200 meters deep and the crater area is 5,466 hectares wide. Ijen Crater Lake is known to be the largest strong acid lake in the world. The main gateway to the Ijen Crater Nature Reserve is located in Paltuding, which is also a Forest Protection and Nature Conservation Post.From Paltuding, you can walk a distance of about 3 km.

The initial trajectory as far as 2 km is quite heavy because it is uphill. Most trails have a slope of 25-35 degrees. In addition to going uphill, the soil structure is also sandy, making the climbers' footsteps heavier because they have to hold their weight so that they don't fall backwards. To go down to the crater, you have to traverse a rocky terrain as far as 800 meters with steep conditions up to a slope of 45 degrees. So, excellent physical condition is highly recommended if you want to go on an adventure to Ijen crater.

In Ijen Crater, there is an eternal blue fire phenomenon. This natural sight only occurs in two countries in the world, namely in Ethiopia (Mt. Dallol) and Ijen Crater in Indonesia. Blue fire can only be seen by the eyes when there is no light. So, the right time to see it is 2 to 4 in the morning. From Ijen Crater, we can see other mountain views in the Mt. Ijen ranges, including the peak of Mt. Marapi which is east of Ijen Crater, Mt. Raung, Mt. Suket, and Mt. Rante.