On forgotten walls of country churches or crumbling castles throughout Ireland, the tiny figures squat unseen. Lost in gray brickwork, obscured by ivy or moss, Sheela-na-gig stone carvings can be hard to spot in the wild — but these medieval creations are in no way coy. Typically bald-headed naked females, with hanging breasts and legs spread wide to display exaggerated vulvas, Sheela-na-gigs at first seem peculiarly out of place in the prim surroundings of a Christian church. However, these envoys from an ancient past have a lot to teach us about Irish and northern European history, and about the pagan roots of the global festival now known as St. Patrick’s Day.