The earthwork presents itself as something resembling a miniature motte and bailey, the kind of fortified mound-and-enclosure arrangement associated with early Norman settlement, yet it almost certainly has no connection to that tradition. What you are looking at is most likely the damaged remains of a prehistoric burial monument, its original form so thoroughly altered by ploughing and levelling that even specialists, comparing field notes from the 1970s against nineteenth-century Ordnance Survey maps, have struggled to agree on what it once looked like. A heel-shaped basal platform, roughly twenty metres north to south, carries a steep-sided circular mound at its southern end with a flattened top. On the eastern face, a narrow indent slopes upward with the appearance of a ramped entranceway, though a low ridge of earth just inside it effectively blocks any direct approach to the upper mound.

Fieldwork visits in April 1970 and April 1977 recorded a very different monument: two conjoined oval mounds set on a longer platform, themselves enclosed on the northwest, west, south, and southeast by an earthen and stone bank with a shallow, flat-bottomed fosse between bank and mound. By a third visit in May 1977, only weeks later, the outer bank had been completely removed and most of the northern mound demolished, presumably by farm machinery. The 1838 Ordnance Survey six-inch map had already recorded a heel shape at the site, but a close reading by David McGuinness, who surveyed the monument in 2015, suggests the surveyors may have been depicting the outer bank rather than the inner platform, and that the heel outline reflects the curve of the southwestern bank as it survived into the 1970s. A more detailed twenty-five-inch map, drawn later in the nineteenth century, shows a pear-shaped central element still largely intact, closer in form to what fieldworkers found in 1970. The current working interpretation is that the site was originally a pair of conjoined bowl-barrows, a type of prehistoric funerary mound typically circular and domed in profile, sharing an oval ditch, with a bank placed further out. Comparable paired arrangements survive more completely at Lakill and Moortown, also in County Westmeath.

The monument sits on the southwestern edge of a hill spur, with the ground falling away sharply to the southwest. Approaching from that direction, it occupies what feels like a high point, though the actual ridge continues further north. The wider landscape around Killucan retains several related earthworks, including a cluster of barrows at Rathnarrow and Lisnabin, suggesting this was once a meaningful concentration of funerary monuments across elevated ground, even if much of the evidence at Rathwire itself has now been reduced to an ambiguous and overgrown mound.