Mount Rinjani, on the Indonesian island of Lombok, is at 3,726 metres the country's second-highest volcano and offers one of Southeast Asia's most magnificent summit treks. Within the vast caldera carved out by the colossal peak lies Segara Anak ("Child of the Sea"), a crescent-shaped turquoise lake left behind by a great eruption thousands of years ago. From the middle of the lake rises the still-living cone of Barujari; this young volcano, smoking now and then, is the beating heart of the caldera. When the steep caldera walls, the natural hot springs along the shore and the summit rising above the clouds come together, the scene resembles another planet.
Climbing Rinjani is a multi-day adventure: starting from the forested foothills with guides and porters, the trail crosses golden savanna slopes to reach the campsites at the rim of the caldera. Here colourful tents line up, sunset falls over the crater, and the sky—far from light pollution—fills with the Milky Way at night. In the small hours, those who climb to the summit over crumbling ash and rock are rewarded by a sun rising above a sea of clouds and the turquoise lake glittering beneath their feet. Bold trekkers descend into the caldera to wash away their fatigue in the hot pools along the shore of Segara Anak.