Climbing down to Kawah Ijen in the early morning hours is like descending through a time portal. Surrounded by sulphur fumes as blue fire ignites, it’s as though you have stepped back into the Archaean age. Kawah Ijen is one of the largest highly acidic lakes in the world, located in the Ijen volcano complex, across the strait from Bali in East Java, Indonesia. Situated on the eastern part of the Baluran National Park, its turquoise water adds a splash of colour to the yellow tinted ashen terrain, both results of the high sulphur concentration. It is most famous for the natural blue flame phenomenon that are only visible at night. The blue flames occur due to the ignition of escaping sulphur gases coming into contact with the oxygen in the atmosphere. They are often shrouded by a veil of smoke and fumes, giving the scene an otherworldly sense. Before the tourist boom, sulphur mining was the main activity in the volcanic crater. Miners can still be seen in the early morning hours balancing sulphur-laden baskets on their shoulders as they climb out of Kawah Ijen. It is one of the few active sulphur mines left in the world, and the miners, frequently photographed by hikers, have become tourist attractions themselves. Indonesia road trip: explore Java’s active volcanoes Kawah Ijen sits inside the highest peak in the volcano complex at 2,799 metres (9,183 feet) above sea level. The trail can be split into three stages: the ascent, walking along the crater rim and the descent into the active crater. The most popular time to start the trail is around 1am. To avoid the crowds, going around sunset is also an option, but the sulphur miners make their trips in the early morning to avoid the heat. On a recent trip to Kawah Ijen it took me two hours to hike in and one hour to get out. We spent an extra two hours around the crater to take in the scenery and wait for sunrise before trekking back out. A ticket is required to enter the national park and costs 100,000 rupiah (US$7), which includes hiking with a tour. The hike can be done independently, but having a professional guide comes in useful for inexperienced hikers and to ensure safety inside the active crater. You will need a gas mask to visit the crater, to protect your lungs, eyes and throat from the fumes. All the tours would provide one, otherwise you can rent one at the base camp. Warm clothes and a flashlight are also recommended for the ascent at night. There is only one main path to the lake, therefore it’s not hard to follow even if hiking independently. The terrain on the hike starts off with fine volcanic sand before shifting to loose rock and then to boulders in the crater. A snack shack marks the end of the climb to the crater rim. This provides a good midway point to rest, with benches and bathrooms, but is not open until sunrise. If the trail proves too much, mountain taxis are available for hire. These so-called taxis are cushioned carts pushed by entrepreneurial locals who clamour for customers between the car park and cafeteria. The price fluctuates around one million rupiah one way depending on the weight of the passenger. They will only take you as far as the crater rim, where the path becomes rocky and steep. The path down is narrow, so stay out of the miners’ way when possible, as they carry heavy loads. The blue flames are best observed from afar, as the sulphur fumes escape the surface at temperatures of up to 600 degrees Celsius (1,112 degrees Fahrenheit). Keep your gas mask on inside the crater at all times and find somewhere safe to sit. Mounting your camera on a tripod makes it easier to capture images of the blue flames using slower shutter speeds, although it can still be difficult because of the constant fumes. My tour guide informed me that hikers have had problems with Nikon cameras because of the high acidity of the gas, so if you have one, you might want to protect it in a bag or leave it at home. The hike up Kawah Ijen can be done year round, and the easiest option is to join a tour from Bali. This would include pickup, equipment and a guide. A tour to Kawah Ijen from Bali usually lasts 24 hours. Where to stay: To do the trek independently, the nearest village to Ijen is Banyuwangi. A comfortable and affordable place to stay is Hotel Blambangan. Staff at any of the accommodation there can help organise transport to and from the car park. Expect to pay around 500,000 rupiah or rent a scooter for 100,000 rupiah. The car park at the base is big but the roads up are windy, so it’s best to hire a driver with a car to avoid driving down after the hike. Getting there: The nearest airport is the Ngurah Rai International Airport in Bali. From Bali, head to Gilimanuk to board the one-hour ferry to cross Bali Strait to Java. It’s about an hour’s drive from the port to the summit.