On the Hill of Uisneach, in a portion of land taken from the province of Connaught, a fortress was erected by High King Tuathal Teachthmar. Uisneach, believed to be the geographical center of Ireland, was, until the reign of Tuathal, the place where all kings were crowned, and the ceremonial site of the celebrations of Beltaine (May Day). Beltaine marked the beginning of summer, the time when the animals were driven out to the summer pastures. Rituals were performed to protect the cattle, crops and people, and to encourage growth. Special bonfires were kindled, and their flames, smoke and ashes were deemed to have protective powers.
It is believed that the Nemedian Druid, named Midhe, lit the first fire there. Countrywide, all household fires would be doused and then relit from the Beltaine bonfire. These gatherings would be accompanied by a feast, and some of the food and drink would be offered to the aos sí (fairies) to ensure a year of good luck and prosperity. In the province of Ulster, Beltaine was known as Lammas, and a fair has been held in Ballycastle, County Antrim, uninterrupted for more than 300 years.
Today, Uisneach consists of a set of monuments and earthworks spread over 2 square kilometers. Around and upon the hill there are the remains of circular enclosures, barrows, cairns, a holy well and two ancient roads. On the southwest side of the hill is a large, oddly shaped limestone rock inside a circular enclosure. It is almost 20 feet tall and thought to weigh over 30 tons. In Gaelic it is called the Ail na Míreann (stone of the divisions,) and it is said to have been the place where the borders of all the provinces met.