Ijen is a volcano complex located in East Java, Indonesia, famous for its blue fire phenomenon, turquoise crater lake, and sulfur mining operations. The trek to the crater is challenging, involving steep and rocky paths, requiring a reasonable level of fitness. Due to the volcanic activity and sulfur fumes, accessibility can be limited, and visitors should wear gas masks (available for rent) and follow safety guidelines. It's recommended to start the hike in the early morning hours to witness the blue fire before sunrise. Solo visits are possible, but hiring a local guide is highly recommended for safety and to learn about the volcano and mining activities. The dry season (April to October) is the best time to visit. The approximate cost, including transportation, entrance fees, and gas mask rental, ranges from $50 to $150 USD. A typical visit lasts around 6-8 hours, including the hike up and down and time spent at the crater.