A roughly circular enclosure, measuring around 47 metres north to south and 52 metres east to west, sits looking out across a stream valley to the south-west, its earthen banks still legible in the landscape after more than a thousand years.

This is a rath, the Irish term for a ringfort, the most common monument type in the Irish countryside. Ringforts were typically used as enclosed farmsteads during the early medieval period, roughly from the fifth to the twelfth century, with the enclosing bank and ditch offering a degree of protection for a family and their livestock. At Lyre, the bank survives to a height of around 1.5 metres on its better-preserved stretches, though it drops to only 0.4 metres to the south-west and is missing entirely to the north-west. A scarp, a steep earthen face rather than a constructed bank, runs along the western side to a height of 1.8 metres, though it has been damaged to the south-west. Traces of a fosse, the external ditch that would originally have accompanied the bank, can still be picked out to the north-west, south, north, and possibly east. There are two gaps in the enclosure: a narrow one to the north-north-west that is probably a later intrusion, and a wider gap to the east, around 2.5 metres across, with stone facing surviving on its southern side, suggesting this was the original entrance. Because the site sits on a slope, the interior has been built up to create a level platform, a practical solution that also makes the whole structure slightly more visible from certain angles than a flatland example might be.