Mount Rinjani

The crater rim appears after two days of climbing through savanna, then cloud forest, then bare volcanic scree. You look down and the geography defies logic: a turquoise lake fills the caldera floor, and from its centre, a smaller volcanic cone rises — a volcano inside a volcano inside a volcano. Segara Anak (Child of the Sea) steams where hot springs meet the lake. At 3,726 metres, the summit of Rinjani catches the first light in Lombok, and on clear mornings, both Bali's Agung and Sumbawa's Tambora are visible on the horizon.

Mount Rinjani is an active stratovolcano on Lombok island, West Nusa Tenggara, and Indonesia's second-highest volcano at 3,726 metres. The 6-by-8-kilometre caldera contains Segara Anak, a 200-metre-deep crater lake, from which the post-caldera cone Gunung Barujari continues to erupt periodically (most recently in 2016). The standard trek is 2-3 days: Day 1 ascends from Senaru or Sembalun to the crater rim (2,641m); Day 2 descends to the lake and hot springs, with an optional 3am summit push; Day 3 descends. The Senaru route passes through tropical forest; the Sembalun route crosses open savanna. Rinjani holds deep significance for the Sasak people (indigenous Muslim population of Lombok) and Hindu Balinese, both of whom make pilgrimages to Segara Anak. Guides are mandatory (arranged through the Rinjani Trek Management Board in Senaru or Sembalun). The trek is physically demanding, with significant altitude gain and steep, loose terrain on the summit approach.