The site at Lisculliheen, known in Irish as Lios Coilichín, is a univallate rath, that is, a roughly circular settlement enclosed by a single earthen bank, of the kind built across Ireland during the early medieval period. What makes this one worth pausing over is what lies inside it: a souterrain, an underground stone-built passage or series of passages typically used for storage or refuge, whose geometry has been quietly collapsing in on itself for some time.

The souterrain is T-shaped in plan and built entirely in drystone, meaning the stonework was laid without mortar. It sits in the northern part of the rath's interior, alongside the foundations of a circular hut. There are two passages. The first runs roughly east-west, measures 2.2 metres long and just under a metre high, and is roofed by three stone slabs; you enter by squeezing through a gap beneath the easternmost of these. A lintelled opening about 1.2 metres along leads off southward into the second passage, but collapse has blocked that branch after only 1.4 metres. The lintelled entrance to this second passage is 45 centimetres wide and 55 centimetres high, its covering stone supported on either side by upright slabs and a few courses of drystone masonry. These are cramped, careful dimensions, and the stonework around that blocked branch speaks to the slow pressure of time doing what it does. The rath itself is skirted on its western edge by a laneway, with a small east-flowing stream running along the northern boundary of the surrounding valley. The site was documented by J. Cuppage in the 1986 Dingle Peninsula archaeological survey, a substantial regional study published under the title Corca Dhuibhne.