Opil de San Marcos Food and drink · Irun, Bidasoa Beherea / Bajo Bidasoa, Gipuzkoa Image of Irun, not of the place itself. In Irun, as in Hondarribia and Errenteria, it is a tradition for godmothers to give their godchildren an opil, a sponge cake decorated with hard-boiled eggs, on 25 April, the feast of San Marcos. 25 de abril Photo: Fotografia enviada per Hugo What to see and do in Irun