Ijen Crater (Kawah Ijen), located on the island of East Java, famously contains the world’s largest acidic volcanic crater lake. By day, the steaming waters of the lake take on a brilliant teal color, and at night, burning sulfuric gases emit a blue glow.
A one- to two-hour leads up the slopes of the volcano to the rim, where hikers are rewarded with spectacular views of the colorful lake and the surrounding Ijen Plateau from 9,450 feet (2,880 meters) above sea level.
While Ijen Crater qualifies as one of Indonesia’s most beautiful natural wonders, it tells a tragic cultural tale as well. For more than four decades, the crater has been the site of sulfur mining activities, and today, the men and women working the crater earn less than 25 U.S. cents per pound through the grueling work of hauling loads of sulfur weighing up to 220 pounds (100 kilos) from the crater floor.
Bondowoso and Banyuwangi both offer a variety of accommodations for travelers planning to hike to the rim of Ijen Crater.