ROSTELLAN, IRELAND—A new study of a stone structure in southern Ireland’s Cork Harbor suggests that it is a megalithic dolmen, and not a nineteenth-century folly connected to Rostellan Castle, as had been previously thought, according to a report in The Irish Examiner. Archaeologist Michael Gibbons said that Carraig á Mhaistin stands at the western end of an 80-foot-long cairn concealed by estuarine mud and rising sea levels. Such cairns may have been built to provide support to portal tombs, he explained. The only other identified intertidal portal tomb in Ireland is in West Cork, on the River Ilen, he added. These tombs may have been part of a wider network of tombs that has not survived in the intertidal zone, Gibbons concluded. To read about a notorious nineteenth-century prison in the middle of Cork Harbor, go to "Letter from Ireland: The Sorrows of Spike Island."