What lies beneath and around that planting, however, is the ghostly outline of an early medieval enclosure, its identity uncertain, its original form now divided and worn almost beyond recognition.

A ringfort, known in Irish as a rath, is a roughly circular earthen enclosure used during the early medieval period, most commonly as a farmstead or place of habitation. The site at Slevoy was recorded on the 1839 edition of the Ordnance Survey six-inch map as a subrectangular enclosure measuring approximately 55 metres west-northwest to east-southeast and 50 metres north-northeast to south-southwest. By the time field investigators examined it more closely, a later agricultural bank running northwest to southeast had bisected the monument, effectively splitting it in two. The northeastern portion survives as a defined earthen bank, four to five metres wide and rising less than a metre on its interior face, while the southwestern half has been reduced to a barely perceptible rise in a harvested cereal field, visible only under the right conditions of low light or crop growth. There is no surviving fosse, the external ditch that typically accompanies such enclosures, and no identifiable entrance. The rectangular rather than circular ground plan, measuring roughly 35 metres by 33 metres within the surviving section, is unusual enough that it qualifies the site only tentatively as a ringfort at all. It may be an altered example, reshaped by centuries of farming, or it may originally have been something slightly different.

The tree planting that now occupies part of the enclosure at least marks the spot, even if it complicates reading the underlying earthworks. The southwestern portion, visible as a crop mark rather than any standing feature, serves as a reminder of how much archaeology survives in Irish fields not as ruins but as faint disturbances in the ground, legible only in the right season and from the right angle.