Grianan of Aileach in the context of "Inishowen"

Ringforts or ring forts are small circular fortified settlements built during the Bronze Age, Iron Age and early Middle Ages up to about the year 1000 AD. They are found in Northern Europe, especially in Ireland. There are also many in South Wales and in Cornwall, where they are called rounds. Ringforts come in many sizes and may be made of stone or earth. Earthen ringforts would have been marked by a circular rampart (a bank and ditch), often with a stakewall. Both stone and earthen ringforts would generally have had at least one building inside.

The Dagda (Old Irish: In Dagda [ˈd̪aɣða], Irish: An Daghdha) is considered the great god of Irish mythology. He is the chief god of the Tuatha Dé Danann, with the Dagda portrayed as a father-figure, king, and druid. He is associated with fertility, agriculture, masculinity and strength, as well as magic, druidry and wisdom. He can control life and death (cf. his staff), the weather and crops, as well as time and the seasons.

He is often described as a large bearded man or giant wearing a hooded cloak. He owns a magic staff (lorc) of dual nature: it kills with one end and brings to life with the other. He also owns a cauldron (the coire ansic) which never runs empty, and a magic harp (Uaithne, though this may be the name of the harper), which will not play unless called by its two bynames, and the harp can fly itself to the Dagda when thus beckoned. He is said to dwell in Brú na Bóinne (Newgrange). Other places associated with or named after him include Uisneach, Grianan of Aileach, Lough Neagh and Knock Iveagh. The Dagda is said to be the husband of the Morrígan and lover of Boann. His children include Aengus, Brigit, Bodb Derg, Cermait, Aed, and Midir.