I had booked the Ijen Crater tour through Quinn homestay. The cost of the tour was 275000 IDR on weekdays and 325000 IDR on weekends which included masks, a tour guide and also a stop at a nearby waterfall. The tour left at 12:15 am and was usually back by 9am.Ijen crater is an active volcanic crater which is also a natural Sulphur mine. It also consists of the world's most acidic lake and the famous blue fire. This place was made famous by Nature documentaries. At least I saw it on one of the BBC/Nat Geo documentaries. The other famous volcano trek that you can do in Java is the Mount Bromo, which is accessible from a town called Probolinggo. I did not end up doing Mount Bromo because of time constraints.The jeep picked me up from my hostel at 12:40 am. I was part of a group which included 15 more people. We proceeded to the starting point for the trek which was an hour or so away. Here we were given masks, head torches and eyewear to protect us from the Sulphur fumes. The hike to the crater was a total of 3 kilometres: 2 kilometres uphill at a steep gradient, followed by 1 kilometre in flat terrain. After this we descended to the crater floor, which was a 200 meter steep descent. We reached the bottom of the crater under the cover of darkness. Here we saw the blue fire produced by the burning sulphur gases. The phenomenon was only visible at night. We also saw how Sulphur was mined in this natural mine. The workers earned about 1000 IDR for every kilogram that they could mine and carry to the valley below. These miners were exposed to the poisonous Sulphur dioxide gas for prolonged periods, as they would usually work without masks. They carried the mined sulphur in baskets which often weighed equal to or more than their body weight. As a result of the recent tourism, to increase their incomes, the miners also made snall toys out of sulphur which they sold to tourists for 20000 IDR.Another site to witness here, was a turquoise lake that had formed inside the crater. This lake was higly acidic due to sulphuric acid generated from the mining and was allegedly the world's most acidic lake with a PH of 0.5.The views from inside the crater at sunrise were surreal. Post sunrise we began our ascent to the mouth of the crater. This was followed by our descent to the vehicles. We were back to the vehicles by 7 am. After this, we were supposed to go see a waterfall as part of the tour but we all opted against it because of tiredness. I was dropped of at the hostel by 9 am.