The enclosure at Lisdachon is subrectangular, an unusual shape for a rath, which already sets it apart from the thousands of more familiar round examples scattered across the Irish landscape. A rath is an early medieval enclosed farmstead, typically defined by one or more earthen banks and ditches, and used as a defended homestead during the first millennium. Here, the enclosure stretches roughly 41 metres on its longer axis and just over 34 metres on the shorter one, with two concentric banks separated by a fosse, the term used for the ditch between them.

Surveys carried out in 1971 and 1976 recorded the site in considerable detail. The inner bank survives well on most sides but has been worn down to a scarp along the north-west. The intervening fosse remains legible in several sections, particularly to the south-west and north-east. A causewayed entrance on the east-north-east side is one of the more precisely documented features: a gap of around four metres at the top of the inner bank leads to a causeway crossing the fosse, roughly five metres wide overall and still standing about thirty centimetres above the surrounding ground. The interior carries traces of cultivation ridges aligned roughly east-north-east to west-south-west, suggesting the enclosed ground was worked at some point, and a faint internal bank runs north-north-west to south-south-east across the interior. A slight rise marks where an Ordnance Survey triangulation station once stood, recorded at 318 feet above sea level. The site has not escaped damage: quarrying has removed part of the exterior on the north-west side, and a field boundary cuts across the north-west quadrant, truncating the monument in that corner.