About 1,200 years ago, a reef in the middle of Lake Titicaca in what is now Bolivia became the repository of a people’s most valued possessions. In 2013, a sparkling cache of those objects was unearthed by underwater archaeologists. Six years later, researchers think they now know what the objects represent—evidence of a religion that helped the Tiwanaku state become a dominant force in the region.

Results of the excavation were revealed in a paper published today in the journal Proceedings of the National Academy of Sciences. Gold objects, metal ornaments, semiprecious stones, and incense burners recovered at the site suggest the reef—located near the Island of the Sun, home to multiple Tiwanaku sacred sites—was once used as