In 1999, archaeologists made a stunning find near the summit of a stratovolcano on the Argentina–Chile border. Three Inca children, sacrificed in a religious ritual 500 years earlier, had been preserved immaculately in the small chamber in which they had been left to die. Due to the dryness and low temperature of the mountainside, the bodies had frozen before they could dehydrate, making them “the best-preserved Inca mummies ever found.” Even the hairs on their arms were intact; one of the hearts still contained frozen blood.

Known as the Children of Llullaillaco, they’re on display today at the Museum of High Altitude Archaeology in Salta.