This is a rath, the most common type of early medieval Irish settlement, typically constructed between roughly the sixth and tenth centuries. A rath consists of a raised circular or oval platform enclosed by one or more earthen banks, the bank itself formed from the material thrown outward when the interior was levelled. They functioned as farmsteads, the bank providing a degree of security for livestock and household alike.

The Drum example is a broadly oval platform, measuring approximately 35.9 metres on its north-west to south-east axis and 31.7 metres across the other way. The enclosing scarp, which is the steep outer face of the bank, rises to about 1.9 metres on the north-east side and 1.7 metres at the south-west. For most of its circuit the external face is relatively vertical, which gives it a purposeful, constructed appearance even after centuries of weathering and grass growth. The exception is a section at the south-south-east, where the scarp eases into a gentler ramp-like slope about five metres wide. That softening of the profile is commonly read as the trace of an original entrance, the point where people and animals would have passed in and out. The interior tilts gently downward from its centre towards the north-east and east. Hawthorn, gorse, and clumps of brambles ring much of the perimeter, with the interior remaining open and grassy, sitting on a low rise in ground that rolls away into undulating pasture and patches of bog.