What makes it quietly unusual is the layering of its defences, a system of banks, ditches, and terraces that steps down the natural fall of the hillside in a way that blurs the line between built fortification and shaped landscape. The site occupies an oval of roughly 52 metres east to west and 35 metres north to south, and the ground itself, steeply dropping toward the river on the south-south-east, becomes part of the defensive logic.

A ringfort, or rath, is an enclosed farmstead of early medieval Ireland, typically dating from somewhere between the sixth and tenth centuries, and usually defined by one or more earthen banks with an intervening fosse, the ditch dug to provide material for the bank. At Lissavane the arrangement is more complex than the single-bank norm. Two earthen banks survive along the western to north-eastern arc, separated by a fosse that is wide and flat-bottomed, measuring around 1.6 metres across. The outer bank is particularly substantial, standing to an external height of around 2.25 metres and spreading to over 7 metres in width, though it is now heavily overgrown with trees. Where the natural ground plunges steeply toward the river, the builders used a series of scarps and terraces rather than built-up banks; an inner scarp of 2.6 metres and an outer scarp of nearly 4 metres are separated by a terrace roughly 3.6 metres wide, with a further terrace of around 5 metres cut into the slope below. A probable entrance opens at the north-east. Quarrying has removed sections of the fosse and outer bank along the western arc, which accounts for some of the asymmetry visible today. At the centre of the interior, a souterrain, an underground stone-lined passage of the kind often used for storage or refuge, opens into the ground, and a depression in the north-west quadrant sits immediately to its west, possibly marking a collapsed section of the same structure.