Chicago-based photographer Reuben Wu traveled to Indonesia to photograph the incredible Blue Fire Crater in Ijen. According to Wu, "the journey into the Ijen Caldera is not for the faint hearted. A two-hour trek up the side of the rocky volcano is followed by another 45-minute hike down to the bank of the crater. The blue fire found at the base is the result of ignited sulphuric gas that burns up to 600 degrees Celsius (1,112 degrees Fahrenheit) and can flare up to 5 meters (16 feet) into the air. It is the largest 'blue flame' area on Earth." While the journey seems incredibly daunting, the resulting images surely made the voyage worth it. Check out some of the awesome pictures below and follow Reuben on Instagram for more jaw-dropping photography.