Why were these people recently carrying decorated skulls through a cemetery in La Paz, Bolivia? They were celebrating Día de las Ñatitas (nya-TEE-tass), a festival observed by the country’s second largest indigenous group, the Aymara, each year. The Aymara believe that these skulls, called ñatitas, house spirits that influence all aspects of life, including money, love, and safety. They’re honored year-round, but during the festival, the Aymara kick things up a notch, adorning them with hats and sunglasses, praying, and leaving offerings such as flower petals. Some of the ñatitas are part of private shrines, while others are acquired from medical schools or old cemeteries. Digging up skulls might sound morbid, but the Aymara see it as a joyful occasion and spend much of the day partying. It’s their way of saying thank you to the dead. “No matter where you are, you think about [the ñatitas],” one participant told National Geographic, “and ask for whatever you want and need: to be good at your studies, for health, and protection.”