Ring of Gullion AONB

The Ring of Gullion is a geological formation and area, officially designated as an Area of Outstanding Natural Beauty, located in County Armagh, Northern Ireland. The area centres on Slieve Gullion, the highest peak in County Armagh, measures roughly 42 by 18 kilometres and comprises some 150 km2 defined topographically by the hills of an ancient ring dyke. Parts of the area have also been officially listed as Areas of Special Scientific Interest.The geological formation was the first ring dyke to be mapped, although its significance was not understood until similar structures had been described from Scotland. It was emplaced during the Paleogene opening of the Atlantic Ocean during the formation of the North Atlantic Igneous Province.

Source: Wikipedia