Mount Rinjani, Indonesia (14/20)

Located on the island of Lombok, Indonesia, Mount Rinjani is the second-highest volcano in the country and one of the most challenging treks in Southeast Asia. At 3,726 meters (12,224 feet), the climb is strenuous, but the reward is worth it: a stunning crater lake known as Segara Anak, where visitors can camp and soak in the natural beauty. The surrounding terrain, with its lush forests and rugged volcanic features, offers a unique hiking experience.