The island of Lombok in West Nusa Tenggara is known for its beaches and coral reefs, but it also has notable inland landscapes. One of the better-known is Segara Anak, the crater lake that lies inside the caldera of Mount Rinjani, within Mount Rinjani National Park.
The name Segara Anak is commonly translated as "child of the sea", a reference often linked to the lake's blue colour, which resembles seawater. Reaching the lake requires a demanding trek, usually over more than one day, from trailheads such as Senaru or Sembalun. Treks need to be registered with the national park, and visitors are expected to go with a licensed guide and porters. Good fitness, warm clothing and enough water are important.
A distinctive feature of the lake is Gunung Barujari, a younger volcanic cone that rises from the caldera next to the water. It is an active vent, and park authorities may restrict access to parts of the area when volcanic activity increases. Near the lake there are also natural hot springs where trekkers often rest and soak their feet after the long walk.
Among the Sasak people and other local communities, the hot springs and the lake are traditionally associated with healing, and some people bathe in them for that reason. These are local beliefs rather than established medical facts. Local tradition also tells of trees and spots around the lake where people come to pray or make personal requests, reflecting the spiritual value the area holds for many residents.
Many trekkers camp near the lake overnight, as the caldera offers views of the water and the surrounding crater walls. Campers should use designated areas, carry out all of their rubbish, and avoid polluting the lake and springs. Weather in the caldera can change quickly and nights are cold, so preparation matters. The lake is also regarded as a sacred place, and local people hold rituals and ceremonies there.
In local belief, Mount Rinjani and its lake are home to spirits, and both Hindu communities on Lombok and the Sasak people hold traditional ceremonies at the lake to honour them. Visitors who encounter a ceremony should keep a respectful distance, dress modestly and ask before taking photographs.