Ijen Crater is a lake crater at the top of Mount Ijen inside the area of Ijen Natural Conservation Park. It's located 10km west of Banyuwangi, East Java Province at 2,386 metres above sea level. The lake is one of the sourest lakes in the world with a pH of 0,5 and it is the biggest crater lake on Java. The Ijen Crater lake is ellipse-shaped measuring 960 by 600 metres with a maximum depth of 200 metres deep it contains a whopping 36 million metres cubic steamy acid water.
The water is covered by fog and sulphur smoke. Many tourists are attracted to the beauty of Ijen Crater. There are several mountains you might see from the Paltuding Post in Mount Ijen such as Mount Merapi, Widodaren, Ranti and Mount Papak.
A common sight at Mount Ijen are the sulphur miners collecting the sulphur near the crater and carrying up to 100kg of the stuff on their backs all the way down. Very dangerous work and the miners have a very low life-expentancy due to the many accidents and the poisonous sulphur air.
If you're planning to visit, the best time is dry season between July to September. When rain season, the trekking way becomes slippery and dangerous. The best time to hike Mount Ijen is at 5am - 6am before the sun rises for the total time you need to go up and down is about 4 hours.
You can start going to Ijen Crater from either Banyuwangi or Bondowoso. From one of those towns you need to go to Paltuding Post by renting a jeep for 3 hours trip. Then continue going on foot for 3 miles. On the first 1,5km the road is ascending steeply after that the road is just a bit slopy and you can enjoy the mountains view here.
The entrance ticket price is IDR 2,000 per person for domestic tourist and IDR 15,000 per person for foreign tourist.