The ringfort at Reynella takes the form of a raised, roughly circular platform, measuring about 24 metres north to south and 22 metres east to west, enclosed by a well-preserved bank of earth and stone. Around that bank runs a fosse, the defensive ditch that typically accompanies such enclosures, though here it has been largely filled in along the stretch running from the east-north-east to the south-south-west. An entrance gap just over two metres wide opens at the east-south-east, and the interior floor tilts gently in the same direction. What gives the site an extra layer of interest is the trace of a large rectangular structure visible to the west of centre, the footprint of a house that once stood inside the enclosure.

Ringforts, known in Irish as raths when formed from earthworks rather than stone, were the standard form of enclosed farmstead in early medieval Ireland, built and occupied roughly between the fifth and twelfth centuries. Thousands survive across the country in varying states of preservation, but this one sits in a cluster of related monuments. A souterrain, an underground stone-lined passage typically used for storage or refuge, lies about 320 metres to the west, and a second ringfort sits roughly 180 metres to the north-north-west. That kind of proximity suggests this was once a more densely settled patch of ground than the quiet Westmeath countryside might now imply, with different households or enclosures forming part of the same local community rather than existing in isolation from one another.