This is a rath, the most common type of early medieval settlement in Ireland, typically dating from roughly the fifth to the twelfth century. A rath is an enclosed farmstead, its circular earthen bank serving as a boundary rather than a true fortification, defining the domestic space of a single family and their livestock. What makes this particular example worth attention is the detail that survives in its stonework and the degree to which it has been recorded with precision.

The enclosure at Ballylin sits on a west-facing slope in undulating pasture, its roughly circular interior measuring approximately 28 metres north to south and 27.5 metres east to west. The surrounding bank is constructed from earth and stone, faced externally with stone, and is best preserved along the northern to southern arc. Along the north-west to north-north-east stretch, the bank widens considerably, reaching 2.8 metres across the flat top, and this is where the stone-facing survives in its clearest form. Outside the bank runs a fosse, which is the shallow external ditch that would have reinforced the enclosure's boundary; here it survives to a depth of around 0.2 metres and a width of 1.2 metres, running from the south-east around to the north. Much of the stone now lying in the fosse has fallen from the collapsed outer facing of the bank, and vegetation has grown thickly over it, softening and obscuring what was once a more defined edge. The interior is level and covered today by mature trees. The site was compiled and recorded by Denis Power, with notes uploaded in August 2011.

The enclosure sits in working farmland, and a field boundary running roughly north to south skirts the eastern edge of the site. Visitors approaching across the pasture should be aware that the fosse is largely hidden beneath vegetation and scattered stone, making the outer perimeter easy to misread as natural ground variation. The bank's external stone-facing is most legible along the north-west to north-north-east arc, where the flat-topped width gives a clearer sense of the original construction effort. The mature tree cover within the interior means that in summer the inside of the enclosure is deeply shaded, while the outer bank reads more clearly in low winter or autumn light when the vegetation has died back.