It is easy to overlook, especially when the lake level is high, but what appears to be a natural island is almost certainly a crannog, an artificial island constructed by human hands, typically during the early medieval period. These structures were built by piling up layers of stone, timber, brushwood, and peat to create a stable platform that could support a dwelling, offering both a defensive position and a degree of social prestige to whoever occupied it.

The mound at Moneyvolan is roughly circular, measuring about twenty-two metres in diameter, and its construction is most legible on the south-eastern side, where a kerb of fairly large boulders, each around half a metre across, remains partially visible. This stone edging would have helped to define and stabilise the perimeter of the platform. The lough itself is a compact, broadly rectangular body of water, approximately four hundred metres along its longer axis, and the crannog occupies the north-western corner, a position that would have made approach by water easy to monitor. No timber features survive above the surface, which is not unusual; wood rarely persists unless it remains waterlogged, and exposed crannogs often preserve only their stone cores.