Mount Rinjani or Gunung Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara. It rises to 3,726 metres, making it the second highest volcano in Indonesia.
On the top of the volcano is a 6-by-8.5-kilometre caldera, which is filled partially by the crater lake known as Segara Anak, due to the color of its water, as blue as the sea. This lake is approximately 2,000 metres above sea level and estimated to be about 200 metres deep; the caldera also contains hot springs.