The rath at Lydacan is not the kind of site that announces itself. Its defining earthwork, a roughly circular bank about thirty metres across, now stands barely forty centimetres high and two metres wide at its best-preserved stretches, and at the northern arc even those slight traces become difficult to distinguish from ordinary ground.

A rath is an earthen ringfort, typically dating from the early medieval period, somewhere between the sixth and tenth centuries, and used as a defended farmstead enclosure for a single family and their livestock. Thousands survive across Ireland in varying states of repair; Lydacan's is among the more eroded examples. What makes it quietly interesting is the palimpsest quality of the landscape around it: a later field boundary was built directly over the bank along much of its southern and eastern arc, which is both the reason the structure has survived at all in those sections and the reason it is so compressed and obscured. The field wall effectively replaced the rath bank as a land boundary, preserving its line while burying its form. Associated with the rath is a souterrain, a type of underground stone-lined passage commonly found beside ringforts, thought to have served for storage, refuge, or both. The souterrain is recorded separately and suggests that despite the poor surface condition of the earthwork, the site was once a more substantial settlement.