Kelimutu is a volcano, close to the small town of Moni in central Flores island in Indonesia. The volcano contains three striking summit crater lakes of varying colors. Tiwu Ata Bupu (Lake of Old People) is usually blue and is the westernmost of the three lakes. The other two lakes, Tiwu Ko’o Fai Nuwa Muri (Lake of Young Men and Maidens) and Tiwu Ata Polo (Bewitched or Enchanted Lake) are separated by a shared crater wall and are typically green or brown/red respectively. The lake colors vary on a periodic basis. Subaqueous fumaroles are the probable cause of active upwelling that occurs at the two eastern lakes.
According to the local office at Kelimutu National Park, the color changes as a result of chemical reactions resulting from the minerals contained in the lake perhaps triggered by volcano gas activity. Kawah Putih lake in West Java, south of Bandung, is another crater lake in Indonesia with some similarities to the lakes at Kelimutu.