Popularly known locally as “Blue Fire”, Kawa Ijen on the island on Java in Indonesia is an hr drive from Banyuwangi (East Java). The hike is roughly 2 miles in length to the highly acidic lake at the center of the crater. The cumulative elevation change (first gain to the rim ~1300 ft and descent to the lake ~700 ft) is around 2000 ft, varying accounts can be found online.
Average time to the crater lake is around 120 mins at the laziest best and similar on the way back. Longer times are partly due to its popularity and the number of fellow hikers you witness in the dark. This may be the most populated hike I have been on to date. At any time expect around 200-400 people on this short hike flashing torches through the night. And I wonder how?
The blue flame is a very pretty sight. Go figure the how!
The trail of lights on the way back as seen above.
Additional pictures of Mt Raung that is part of the wider volcanic belt.