Iron Age saunas, unique to the Castro Culture of northwestern Iberia, have puzzled archaeologists since the nineteenth century. Initially interpreted as kilns, crematoriums, or ovens, their function has since been established as bathing structures; however, the social significance of these saunas has yet to be firmly established. This study provides a new approach to understanding the ways in which Castro communities utilized specialized buildings to serve specific needs related to ritual cleansing and protection. Through an analysis of their placement, structure and decoration, I argue that these buildings functioned to purify and protect people of Castro communities from spiritual and physical danger. Members of Castro society inhabited a world buffeted by the shifting political and economic powers of the Iron Age. The bath structures under study, covered in apotropaic symbols, functioned in liminal spaces to cleanse and prepare Castro people for the dangers that awaited them beyond the walls of their communities and neutralized any potential spiritual contamination they may have acquired upon their return.