Kelimutu ([kəliˈmutu]) is a volcano, close to the town of Moni in central Flores Island of Indonesia containing three summit crater lakes of varying colors. Tiwu Ata Mbupu (Lake of Old People) is usually blue and is the westernmost of the three lakes. The other two lakes, Tiwu Nuwa Muri Koo Fai (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 red in color, respectively. The lake colors do vary on a periodic basis. Subaqueous fumaroles are the probable cause of active upwelling that occurs at the two eastern lakes.
The lake have been a source of minor phreatic eruptions in historical time. The summit of the compound 1639-m-high Kelimutu volcano is elongated two km in a WNW-ESE direction; the older cones of Kelido and Kelibara are located respectively three km to the north and two km to the south. The scenic lakes are a popular tourist destination. Keli Mutu is also of interest to geologists because the three lakes are different colors yet reside at the crest of the same volcano. Kawah Putih lake in West Java, south of Bandung, is another crater lake in Indonesia with some similarities to the lakes at Kelimutu.
According to the local officer at Kelimutu National Park, the colour changed by chemical reaction of any minerals contained in the lake in triggered by volcano gas activity. The closest airports are Maumere, and Ende. There are regular flights to Maumere from Bali. The drive from Maumere to Moni, the town at the base of Keli Mutu, takes about 3 hours.