I have heard the name of Lake Kelimutu since I was a child, so glad I was able to visit it in 2019. Never regret, a unique place, not too difficult to reach.

Kelimutu volcano is located 50 km east of Ende, central Flores on a road that climbs through several small villages and rice terraces into a dense rainforest near the summit. The volcano is in a national park, and there is a fee to enter: not much for locals and foreign Indonesian work visa holders, and more for tourists (about US$15). From a parking area a few hiking trails go up to the summit, which features 3 steep-sided craters with actively roiling multi-colored lakes. On a clear day you can see gases bubbling to the surface and a sulfide scum on the surface of the first two lakes. The local lake names are Tiwu Ata Bupu (Lake of Old People - blue), and the other two lakes, Tiwu Ko'o Fai Nuwa Muri (Lake of Young Men and Maidens - bluish-green) and Tiwu Ata Polo ("Villany" Lake - red) are separated by a shared crater wall. The lake colors are attributed to gas & steam vents on the bottom of two of the crater lakes that discharge CO2 and H2S gases from a magma chamber deep beneath the mountain. The lake colors change throughout the year due to different chemical oxidation and reduction reactions between rain water, ground water, the amount and composition of the rising volcanic gases, and the abundance of iron and manganese. The colors in the lakes change independently from each other, suggesting that each crater lake has its own unique connectivity to the underlying magma chamber.