Geophysical surveys off the coast of County Mayo have revealed a perfectly preserved Neolithic timber-circle submerged under six meters of seawater. The structure, consisting of forty upright oak posts, was protected for millennia by layers of marine silt and peat. It is part of a larger ritual landscape that became submerged as sea levels rose following the end of the last glacial period.
Archaeologists believe the circle was used as a calendrical monument to track the winter solstice. Radiocarbon dating of the timber suggests the site was in active use around 3000 BCE. The discovery is being hailed as the 'Irish Seahenge' and provides a vital link in understanding the migration of megalithic and timber-building traditions between the British Isles and mainland Europe.