The site sits southeast of St Mary's Church in Dromgower, County Kerry, and occupies a position with open views in all directions, the kind of placement that was rarely accidental in early Irish settlement. A ringfort is a roughly circular enclosure defined by one or more earthen banks and ditches, used in early medieval Ireland primarily as a defended farmstead, though some served more communal purposes. What makes Lisderg quietly unusual is the density of occupation within its boundary: four separate stone house-sites survive inside the one enclosure, suggesting this was something more than a single-family holding.

The enclosing bank is substantial, 5.5 metres wide and rising 1.6 metres on its outer face, though only about 0.9 metres above the interior floor, which sits at roughly the same level as the land outside. Within the enclosure, the structures vary considerably in size and form. In the western sector there is a sub-semi-circular enclosure that curves in against the main bank, and about 2.6 metres to its north sits a small rectangular enclosure measuring 4.2 by 3.5 metres externally, with walls 0.6 metres thick. The largest of the four house-sites lies to the southeast; it is sub-rectangular, measuring 8 by 7.4 metres externally, with walls approximately 1 metre thick. Loose stones elsewhere in the interior hint that still more of the original layout may have partially survived, or partially collapsed into the ground. The full dating of the site remains unresolved, as the name Lios Dearg and the structural evidence together point to early medieval origins, but the record does not pin down any closer timeframe.