It is a small act of administrative geography with lasting consequences, and it makes the ringfort at Ballytarsna one of those places where you can read competing layers of land ownership directly in the ground beneath your feet.

A ringfort, sometimes called a rath, was typically a farmstead of the early medieval period, roughly 500 to 1000 AD, enclosed by one or more circular banks and ditches to provide security for a household and its livestock. The example here sits on an east-facing slope of a north-south ridge, set within undulating tillage land with open views in all directions, the kind of position that would have suited both defence and daily farming activity. The enclosure itself is slightly raised and broadly oval rather than perfectly circular, measuring 23 metres north to south and 34 metres east to west internally. Around it runs an earth and stone bank, still standing to an external height of 1.7 metres in places, though it projects only modestly above the interior. Beyond the bank lies a wide outer fosse, a defensive ditch, measuring seven metres across at the top and still readable at the southern arc of the site where the later boundary line has not touched it. A causewayed gap of about 2.2 metres in the bank at the south-east is thought to be the original entrance, a narrow break left deliberately in the earthwork to allow passage in and out.