This is a rath, the most common type of early medieval Irish enclosure, typically a circular or oval area defined by one or more earthen banks and ditches, used as a farmstead or residence by a family of some local standing. At Lisquigny, the dimensions are considerable: the enclosed area stretches roughly 58 metres along its longer axis and 31 metres across, with the outer face of the bank rising between three and four metres above the surrounding ground, and the scarp at the north-northeast reaching 4.3 metres at its highest point.

The site appears on McCrea's map of County Monaghan, drawn in 1793, and was recorded again on the Ordnance Survey six-inch maps of 1834 and 1907, meaning it has been a recognisable feature of the landscape for at least as long as systematic cartography has covered this part of Ulster. The earthen bank is around six metres wide, the fosse or encircling ditch is preserved to a depth of about 1.5 metres to the north and northwest, and an outer bank or field boundary continues from that same arc around to the east. Mature deciduous trees have been planted along the scarp, which partly explains why the structure reads more like a wooded rise than a monument when seen from a distance. A wide entrance gap, roughly seven metres across, faces east-southeast.

The working farm that has grown up around the base of the rath is part of what makes Lisquigny quietly interesting. Buildings press against the scarp to the east and south, and the lane passing on the southern and northwestern sides has long been shaped by the monument's presence rather than the other way around. The rath has absorbed the centuries without being tidied up or fenced off into abstraction, which gives the place an unforced continuity between early medieval earthwork and the agricultural landscape it has never quite stopped being part of.