In 1936, Leonidas Bernedo Málaga reported the discovery of a large collection of petroglyphs near the village of Illomas. We present the results of a recent study of the site, describing both the rock art and the organization of its surrounding ceremonial complex in light of our broader understanding of the prehistory of what is now the Department of Arequipa. Used for almost three thousand years, Illomas changed in function as population significantly increased in the region by the end of the Middle Horizon. Illomas, as well as other petroglyph sites in this rock art-rich region, was an important locus of worship and aggregation that has been underexplored by the broader archaeological community.