Mount Kelimutu stands 1,639 meters above sea level, roughly 50 kilometers east of Ende on the island of Flores. Its summit holds three volcanic crater lakes, each with its own name and spiritual purpose. Tiwu Ata Bupu, the Lake of Old People, sits on the western side and is usually blue. To the east, separated by a thin shared crater wall, lie Tiwu Ko'o Fai Nuwa Muri, the Lake of Young Men and Maidens, and Tiwu Ata Polo, the Bewitched Lake. The Lio believe that when a person dies, their soul migrates to the lake that matches their life. The elderly go to the cold waters of Tiwu Ata Bupu. The young find warmth in Tiwu Ko'o Fai Nuwa Muri. And the wicked are consigned to Tiwu Ata Polo, the enchanted lake, where the water frequently turns a deep, unsettling red.

What makes the lakes change is both mundane and remarkable. Volcanic vents on the lake floors release gases and minerals into the water, altering concentrations of iron, manganese, and other elements. As these concentrations shift, so does the oxidation state of the water, which determines its color. Iron-rich water turns red or brown. Dissolved minerals in different ratios produce greens, blues, whites, and blacks. The two eastern lakes, despite being separated by a crater wall just meters wide, often display completely different colors simultaneously. One might glow emerald while the other broods in dark chocolate. The first recorded eruption at Kelimutu occurred in 1865 and lasted more than five years. The most recent volcanic activity, a series of minor phreatic explosions, took place in June and July of 1968. Since then, the volcano has been quiet, but the lakes continue their restless transformations.

Kelimutu National Park protects far more than its famous lakes. Mount Kelibara, the park's highest peak at 1,731 meters, anchors a landscape of montane forest that shelters species found nowhere else on Earth. The endemic Begonia kelimutuensis grows in the park's understory, alongside turuwara rhododendrons and arngoni vaccinium. A 4.5-hectare arboretum preserves 78 tree species from 36 families, a miniature catalog of Flores's botanical diversity. Javan rusa deer move through the lower forests. Red junglefowl scratch in the leaf litter. Two montane rodents, Bunomys naso and Hainald's rat, are among four mammals found only within the park's boundaries. The isolation of Flores, strung along the volcanic arc of the Lesser Sunda Islands, has produced this pocket of life that exists in a world of its own.

Most visitors begin the climb to the crater rim in darkness, leaving the small town of Moni well before first light. The reward is watching sunrise hit the lakes. As light spills over the eastern ridgeline, the water surfaces ignite with whatever color they happen to be wearing that morning. The Lio named this place well: keli means mountain, mutu means boiling. The mountain that boils. Even on calm days, the lakes seem to simmer with internal energy, their surfaces shifting between opacity and translucence as gases escape from below. The colors are never guaranteed. Visitors who return years later sometimes find a landscape unrecognizable from their photographs. The lakes have their own schedule, indifferent to human expectation.

The annual ceremony on August 14, known as the feeding of the forefathers' spirits, is the most important ritual in the Lio calendar. Families ascend together, bringing the foods their ancestors loved. They dance on the volcanic slopes. They pray. The ceremony predates any outside religion and persists alongside the Catholicism that Portuguese missionaries brought to Flores centuries ago. For the Lio, there is no contradiction. The dead are simply somewhere specific: in the blue water, in the green water, in the red. The lakes hold them. And once a year, the living climb up to make sure they are not forgotten.