Juanita was only 12 or 13 years old when she walked up a wooden staircase and onto the snowy summit of Ampato (6,380 meters), accompanied by Inca priests intent on making a sacrifice to the apu, or mountain god, of Ampato. She wore a feathered headdress and an elaborately woven shawl and skirt, decorated with pieces of gold jewelry.

An Inca priest gave her a narcotic potion, which probably put her to sleep after days of fasting—and then killed her with a single, precise blow to her forehead. Juanita was wrapped in a fetal position and surrounded by ceramic pots containing food, figurines made of gold and carved wood, textiles, and other objects needed for the afterlife. Then the tomb was sealed with carved rocks—and, over time, by snow as well.

After being frozen in ice for five centuries, Juanita’s concealment came to an end when a neighboring volcano, Sabancaya, began showering ash onto Ampato’s summit. The gray ash absorbed the sun’s warmth and gradually melted snow, uncovering a trail of curious objects that would eventually lead archaeologists to Juanita’s tomb.

First there was a round ceremonial square, made of stones, that climber Miguel Zárate discovered in 1989 on a ridge at 5,000 meters. In a subsequent trip, Miguel discovered ceramics and bones at 5,800 meters, along with the remains of wooden stairs.

Miguel knew that there was probably a tomb atop Ampato because his father, Carlos Zárate Sandoval, had run into similar evidence before discovering the tomb of an Inca princess atop Picchu volcano in 1964. Miguel went to see high-altitude archaeologist Johan Reinhard, of Chicago’s Field Museum of Natural History, who had spent more than two decades uncovering Inca tombs atop Peru’s highest peaks without ever finding a well-preserved mummy.

Zárate and Reinhard returned to Ampato in September 1995, accompanied only by a burro driver, and they retraced the path the Inca priests probably took on their way to the summit. They knew they were on the right track when they discovered bits of rope, ceramics, and wood. But the real breakthrough came in the thin air near the summit, when Miguel spotted a fan made of red feathers poking out of the snow.

Juanita’s stone tomb had melted out of the snow on the summit ridge and slid downhill toward the crater, scattering the fan, gold plates, and three figurines made of silver, gold, and spondylus shell. But the mummy was nowhere to be seen.

To locate Juanita, the climbers wrapped rocks in yellow plastic and rolled them downhill. Near where the rocks came to rest, they found Juanita, who was still wrapped in her Inca shawl even after her 60-meter roll down a snow slope into the crater.

After a few days of work, Miguel and Johan carried the 36-kilogram mummy to the base of Ampato and then on to the village of Cabanaconde, where she was driven to Arequipa and eventually flown to John Hopkins University in Baltimore, Maryland. The fact that the Inca climbed to 6,380 meters, sacrificed children in the snow, and then buried them in bizarre and elaborate tombs made front-page news around the world.

Juanita’s mummy has allowed scientists to understand what she ate, what her health was like, and who her living relatives are.

Reinhard discovered three other mummies, though less well preserved, in subsequent trips to Ampato’s summit (it turns out the stone platforms discovered by Miguel Zárate on the summit were the ceilings of tombs). Based on archaeological evidence and Spanish chronicles, Reinhard and other archaeologists believe the Inca sacrificed children as part of capac-cocha, a ceremony meant to appease the apus, or mountain gods. The purpose of this ceremony was to ensure good rains, but it was also used during earthquakes, volcanic eruptions, droughts, floods, or other times of crisis.

Each child was carefully chosen (on the basis of beauty, innocence, and intelligence), taken to Cusco for a ritual, and then paraded through towns on the way to the mountain. Participation in capac-cocha was an honor for the families because the child, after death, became a spiritual go-between for the people and their apus, still venerated across Peru, though offerings these days consist mainly of coca leaves and chicha.